How about trust ratings with an expiry date?
Say, I'd like to flag someone's offer as not trustworthy.
On the other hand, it's not like I would necessarily consider the person in question a serial scammer.
An easy solution could be to give that person a negative trust rating for the next two weeks™, so that in effect the offer would come from a person with a trust warning.
After some time, when the offer is no longer open, the negative trust is no longer required and thus could expire.
This is interesting. But instead of an expiry date, maybe decreasing as time passes? Reminds me of Gauntlet Legends life points in the arcade. (Pardon the reference for those of you who didn't play this game in the arcade.)
We'll play with this idea and forum reputation will be in plugins so that developers can implement different plugins based on what they need.