Was thinking of this in terms of the offers and wanted in particular, but it could be used through the rest of the forum I think too.
If we had some sort of user voted reputation system for members, it would be a good way of knowing if they are trustworthy or not. For instance, I have had a trade with a member of the forums and it goes well, I can increase their rep to show they are trustworthy. If I find a user is answers a question well, I can increase their rep to show that they are a good source of information.
Not sure what is possible or if this is a good idea, but thought I would put it out there and see what the forums think.