I'm not saying WoW is a bad example and it probably has a point over some other online games but it has had and probably still has many kinds of ways of multi-account abuse. You can use your 2 accounts to farm honor in many ways including killing your other faction character(s) with your character(s), going to the multiplayer battlegrounds and forcing the other side to lose for example by taking the flag somewhere where it can't be reached or you could just fill the BG with your own characters by multiqueue. Gold farming uses the 2 factions and neutral AH for transfering and I'm sure for lots of other things.

Honestly honor farming doesn't accomplish much, you can buy certain tradeable materials with it, sure, but in most cases the time cost compared to some other kind of farming seems like it would be a waste. How profitable it is changes vastly based on expansion as well.

Then there is the whole "multiboxers" issue where people can with few simple steps control 5 identical characters running on top of each other with 0 delay which is totally unfair. Can be used to boost leveling, PvP and honor farming, even some instances...

I've never seen multiboxing used for much of anything except running around in world pvp or battlegrounds and one shotting people for fun, straight up kills provide very little honor and considering most of the battlegrounds are much larger thna 4 or 5 characters and the vast majority of honor comes from winning, it doesn't make much difference in farming value over one character. Multiboxing is only good for using the same characters to say, cast the same spell all at once anyway, using them in an instance would be a nightmare at best.

For the multiaccount problem I can't say anything but there's no solution you could hardcode into your game or completely design around the problem. People that want to will be able to find a way to abuse even if you take extreme measures in preventing it and block huge amount of legitimate players out of the game because of that.

Like I said, its a fools game to spend your time trying to stop the people that are "cheating" instead of banning people for being bad you should just stop them from being able to be bad in the first place.

I've never seen multiboxing used for much of anything except running around in world pvp or battlegrounds and one shotting people for fun, straight up kills provide very little honor and considering most of the battlegrounds are much larger thna 4 or 5 characters and the vast majority of honor comes from winning, it doesn't make much difference in farming value over one character. Multiboxing is only good for using the same characters to say, cast the same spell all at once anyway, using them in an instance would be a nightmare at best.

I have personally seen many kinds of behavior on BGs and the stories I've heard...Especially on private vanilla/TBC servers where each multibox account don't cost money and leveling is fast there are loads of abuse and honor farming. Yes, people do bother with it and things can be minmaxed and optimized to make it profitable thus why people do it.

http://www.wow-one.com/forum/index.php?app=core&module=search&do=search&fromMainBar=1

Note that even when you say multiboxer "one shots people for fun" you have to understand it still ruins the gameplay experience for those other people and this is unwanted and problematic behavior. It arises quite a bit of discussion, but Blizzard allows it. The only thing that keeps multiboxing marginal and saves retail WoW from it is that you'd need to pay subscription fees for each of the accounts and not many people want to invest in it.

http://us.battle.net/wow/en/search?f=post&forum=984270&q=multiboxing&sort=popularity&dir=d

The multiboxing scene is far more blown out than what you might think from your everyday experience in WoW because there are simply so many players that do not multibox. Multiboxers actually try to keep what they do secret in order to avoid player griefing. And yes, instances can be multiboxed as well and it happens in current WoW. People use setups like 1 tank, 1 healer and 3 identical dps with keyboard software and macros to practically control all chars from single screen:

http://www.google.com/search?q=multiboxing+wow+instances+site:www.dual-boxing.com

I have personally seen many kinds of behavior on BGs and the stories I've heard...Especially on private vanilla/TBC servers where each multibox account don't cost money and leveling is fast there are loads of abuse and honor farming. Yes, people do bother with it and things can be minmaxed and optimized to make it profitable thus why people do it.

I wouldn't bring up, or honestly care about private servers, that really isn't a symbol of how detrimental something is to the gameplay in the actual game.

Most of the money gold farmers make is farming low level things like rare pets or gathering materials, these are things that are easier to bot and don't even require multiple accounts, multiboxing doesn't serve much of a practical purpose that I can honestly see.

Note that even when you say multiboxer "one shots people for fun" you have to understand it still ruins the gameplay experience for those other people and this is unwanted and problematic behavior. It arises quite a bit of discussion, but Blizzard allows it. The only thing that keeps multiboxing marginal and saves retail WoW from it is that you'd need to pay subscription fees for each of the accounts and not many people want to invest in it.

No offense but I'd make a stark contrast between people actually making game breaking abuse out of multiple accounts and people just being jerks with it. People being jerks with it is something the OP obviously would not have to tolerate in their game, I would say people being annoying is much less important than physically detrimenting the game or its economy as well.

The multiboxing scene is far more blown out than what you might think from your everyday experience in WoW because there are simply so many players that do not multibox. Multiboxers actually try to keep what they do secret in order to avoid player griefing. And yes, instances can be multiboxed as well and it happens in current WoW. People use setups like 1 tank, 1 healer and 3 identical dps with keyboard software and macros to practically control all chars from single screen:

Honestly even if someone has the ability to run every instance with one computer, you get little out of instances besides gear, perhaps enchant materials, and multiboxing isn't botting, you still have one person having to tediously run the entire dungeon over and over. Not to mention in actual WoW there are limits on most of the good things you can get like the lockouts on heroics unless you random queue.

The only place that makes any kind of tangible money from instances in WoW would be raiding, and if you can show me a multiboxer or multiboxers that can raid I would say they deserve that money because that would be a feat of epic proportions.

Anyway this whole conversation doesn't apply that well, multiboxing only works on games like WoW where its a dynamic combat based world where you actually get useful ability out of synching up attacks and such, it's not like it would help for farmville or something.

I wouldn't bring up, or honestly care about private servers, that really isn't a symbol of how detrimental something is to the gameplay in the actual game.

Whether you care about it or not, private server issues are actually more relevant to the OP's situation assuming he won't be charging subscription fees. With free accounts you are always bound to get more of trolling and abuse that more or less ruins the experience for other players. If you only played retail WoW you haven't begun seeing the problem OP is addressing.

Doesn't serve any point to argue about if multi account is problem for WoW, other online games or OP's game because it is taken for granted in the thread opening post that it is and OP is only trying to find solutions for it. So let's focus on how to fix it.

Log every action players do that can affect others. Establish a path of trades. "This account has traded with these accounts which traded with these accounts". Aggregate that information so you can quickly view who is trading away.

Offer players rewards for reporting gold sellers.

When the player reports them, immidiately go upstream and investigate every account they're related to (Who they've traded with). If they're fraudulent, lock them from trading (in a way where they receive no warning), but don't ban them. When they try to trade, log who they are trading with, and investigate those accounts as well. Once you have a sizeable list of people, ban away.

Look up gold seller sites yourself. If you see your game on there, buy gold, ban all the related accounts that try to trade with you, and reject the credit card transaction. (I know an MMO that did this, and it worked pretty well).

Also log how much of the money in the econemy is being generated in what way. Gold farmers make a living finding the most efficient method possible, and farming it. If you nerf it, you're directly hurting their profits.

It's impossible to detect those. Imagine the following scenario, player A plays game, likes the game, tells player B. Player B joins doesn't like the game but instead of simply quitting the game they set up a farming script/bot and give all the farmed loot to player A because they are friends. Since they are two completely different people/computers/IPs etc there is no possible way to link them by physical hardware/connection. This scenario is completely indistinguishable from a single player who is determined to multi.

You really only have two options and neither are particularly good.

First, you can design the game such that all interaction is with algorithmically selected players. If game play contains matches, then use a match making system so players can't select their multi for an easy win. If you have a trade/shop function then items are traded/sold anonymously so they can't sell/trade items with their multi for free. This solution sucks because players can't do anything meaningful with friends.

The second is to Monitor player to player interaction watching for multi abuse behavior. This one sucks because action can only be taken on multi abusers after a human analysis the behavior and determines it to be multi abuse, it can also make it more difficult for generous players to feel safe giving welcome packages, or for clans to work together as those types of actions would be flagged by the monitoring algorithm. It also leads to every single multi abuser banned starting a forum thread about how it's unfair that they can't play the game with their "family".

Design the game such that new accounts are at a disadvantage? New accounts for example, can't trade any of their starting resources. That at least prevents the case of someone creating multiple new accounts and then just sending the default resources over to their main account.

Repeat trade taxes?, so an account that constantly gives resources to another account does so at a higher and higher tax rate. This goes down if the other account trades a resource to the original account. (Example: Player A has 100 Iron, trades 100, gets taxed 10 for the trade, then generates another 100, then tries to trade it again, gets taxed 20, and so on until only a trickling amount of iron gets to Player B, until Player B actually gives some sort of resource to Player A, and even then it only resets up by an amount that is traded, so they can't just give 1 wood to Player B and have the tax reset to 0)

If it's a game about killing other players, assign players a worth. New players are invulnerable or worth negative points to kill. Killing the same player repeatedly is worth less and less to the killer, even to the point of being negative. That should help stop battleground honor abuse.