@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?
@J I was thinking that it would just be more work than the gold farmers would want to deal with. It's not as clean as gold and so maybe there would be less desire to do the "gold farming" thing. Just a guess though. There is no central thing of value anymore and everything is equally valuable (for the most part). If the players just agreed that rice was the most common need and easy to make by most, then that would encourage "gold farmers" to make rice I guess.
I agree that making bundled trades can help mask any imbalances in the trade. Sure a horse is more valuable then a cow alone, but a cow and 3 chickens can = a horse. However this, as you have shown, complicates matters This is the main part where I think automation can really help, but the details of how it's implements would make or break it.
If I was a player and I needed 10 iron the first thing I'd want to do is just type iron in a search box to bring up every trade that has iron in it. Maybe an option that only shows acceptable trade items that I have in my inventory to get exact matches? Then I decide if it's doable or not? Like you said listing everything you'd accept would be a pain. Maybe as a player putting something on the trading post I list things I WON'T accept? This should be a shorter list you'd think. It would automatically select the same things I'm putting up on the trading block as that wouldn't make sense to accept the same things I'm putting up to trade.
Someone makes an offer and it automatically shows me no matter where I am. I can Accept/Decline/Decline w/reply where I can say why. Would we get a ton of silly offers to weed through from someone just being stupid? : / Lots to think about with this system.