@Angle I do wonder if players would come up with some kind of common item as currency (rice in your example). Your example of needing a horse and a cow are good examples, but I guess I wouldn't see those 2 people being able to barter just those 2 items or maybe a horse and a cow are equal to those people if they both need the other bad enough? On one hand I feel like a barter system can solve some problems and make getting resources you need more interesting. On the other hand I fear it would consume most of the gameplay, which for sure isn't what I want.
@sun In NeoPets did this bartering end up taking a lot of time and take away from other gameplay?
Players tend to come up with not one, but half a dozen common items usable as currency. A Tale In the Desert is another game I think of in terms of bartering, because that game did not have money of any kind, nor did it have a searchable automated barter system If you wanted to trade, you said so on the trade channel, worked out the details in PM, then it could take quite a bit of time and effort for the two players to physically get together to trade because of the difficulties of travel and transporting bulky items in a limited inventory. The main effect of this high time cost was to discourage people from trading with anyone but their neighbors. But there were several standard currencies that emerged - bricks, flax and linen were the three things everyone needed thousands of and got tired of making, so they were a medium-value currency. Firewood was a low value currency because it was gathered, not made - everyone needed firewood, and even the newbiest player could gather it almost as fast as a high level player. It was pretty common for a newbie to trade 1000 firewood for a tool they had no ability to make on their own.
NeoPets on the other hand is a social gaming site. For social gaming sites in general, such as GaiaOnline, Flight Rising, and many others, playing the marketplace and trading is considered to be a legit part of the gameplay. So it's kind of a mis-targeted question if you ask whether people spend time on that instead of other gameplay, because they're _supposed_ to. I earned half the money I have in Flight Rising by making use of the conversion rate between in-game currency and cash-shop currency. I LOVE games where cash shop currency can be sold directly to other players for in-game currency. Buy low, sell high, pretend you are on Wall Street! Will you make a killing or lose your shirt if you buy up all of one kind of item to temporarily force their price up and try to resell yours at the higher price?
And on Flight Rising, one of the main things people are trading are dragons, each being pretty much unique, and therefore even if you're selling for pure in-game currency you need to negotiate what it's worth. People do dragon flipping too - buy one that they think is underpriced and immediately try to resell it for more.
The easiest solution for people would probably be to just have two sets of items in their storage account, things to keep and things to sell.
Then when someone needs something he types the name and how many of it into a search, if there is any account which contains that inside the 'for sale' set he can move a few things from his 'for sale' set into an offer box, everyone else which 'for sale' set contains it gets a message next time they are online, the first that clicks accept gets the trade. Then maybe allow counteroffers with showing the 2 boxes with offered and wanted item and 2 boxes with all other items in these 2 peoples 'for sale' sets and allowing to drag and drop stuff around and click counteroffer which in turn notifies the first person who can accept or decline.
The problem is then people would maybe feel spammed by all those offerings and reofferings while they maybe just want to kill some monsters at that time.
I quite like this idea. Just don't make the offerings and reofferings notifications or messages and you will solve the spam problem. Instead make there be a passive part of the GUI where it displays the fluctuating number of relevant offers and reoffers, and the player has to actively click that to see a list of all the currently available ones they can respond to (or make new ones). Also, don't make the ability to list offers limited to what's currently in the player's inventory.