Trading: Sell/Buy Orders Social addon
 

Is it possible to make an addon that interacts with other characters on a realm-specific basis?

People keep asking for buy/sell orders to be added to the AH UI in developer interviews. Can it be done with an addon first?

It can work like in-game message board pretty much. Someone makes a post asking for so much for an item, and then someone else can CoD them the item in the mail

There can even be a specific system that can track people's records, so you know which sellers are reliable / sell a lot or which buyers are reliable / buy a lot.

Is this possible?

Not really. There's no way to for an addon to communicate with "everyone". Addons can only communicate with (a) your guild over the guild addon channel, (b) your group over the party, raid, or battleground addon channels, or (c) a specific person over the addon whisper channel. In order to share information with "everyone" your addon would have to send addon whispers to every single person you saw, which would probably hit the anti-spam rate limit, and waste a lot of bandwidth anyway since most people you see would not have the addon installed.

There's also the fact that there is no shared "cloud storage" for addons, so your copy of the addon must store its own database locally on your computer, the same way every other addon stores settings and data, and there's no practical way to sync your database with "everyone". Syncing data like that with just your guild is hard enough; for an example, see the complexity of code in addons that broadcast info about the guild bank contents so that everyone in the guild can see the bank without having to visit it, and syncing ratings would be even more complicated.

A simpler solution (and one that's been discussed before, though I don't know if anyone ever implemented it and released an addon for it) would be to have an addon periodically advertise your tradeskill in Trade chat, give you a GUI for setting the price of items, and accept orders via whisper in a certain format (eg. they whisper "!getprice 5 [Awesome Item]" and your addon responds with the price you set for 5x Awesome Item, or they whisper "!codme 5 [Awesome Item] 25g" and your addon alerts you that someone is offering you 25g for 5x Awesome Item). If the other person had the addon installed, it could provide them with a GUI for checking your prices and placing orders, so they didn't have to type the whispers out themselves.

Granted "simple solution" is a bit of a misnomer, as this would not be a simple project by any means, and I have absolutely no interest (or time) to work on such a project, but it would be (sort of) possible.

I agree, this sounds like a big boy to create but.. It would be awesome. Like a trade channel revolution!