The concept is simple and wouldn't be too difficult to implement. Basically, there would be an option to leave feedback after sending or receiving forum gold. The seller and buyer (or, in the case of services, the person offering the service and the person requiring the service) would give each other a general rating based on various factors, eventually resulting in an average that could then be viewed. I would suggest a simple zero to five star rating, but it could be made more complex as well in order to convey more information about that particular buyer or seller. A history of past transactions could then also be viewed.
The goal is to rid the trading sections of people asking about various users, and to provide a trustworthy guide to whether a trader or seller is trustworthy or not.
Obviously, there will be people who, in an attempt to "troll" will give poor feedback. In order to resolve this, the poor feedback could be either completely ignored (in which case, after many more trades, the feedback would be outweighed by positive feedback) or there could be a small mod team put together to review cases (this would work much like the S/A forums).
I believe this would be an excellent way to prevent scammers from going on long sprees, and would help to prevent people who are new to the site from getting scammed.
Edit: Now, I admit that given the personality traits that many users have on JSP, the ratings system would not be perfect. However, no rating system is perfect - there will always be users that wish to tarnish another persons appearance. What is important is that this system would be easier to control and more accurate than user-created systems currently in place.
Regardless of your vote, please leave a brief explanation, I would like to toss around ideas (especially for those that vote no).
Edit:
In response to comments regarding abuse:Quote
There are ways to prevent that abuse though. The main way it would be abused would be people who are looking to pad their reputation. Now, I would bet the average user makes approximately 50 - 100 traders per month. If you limit the amount of feedback that one account can leave for another per day or per month, you could control people who have multiple accounts (or friends) from padding their rating.
This post was edited by Furthur on Jan 29 2012 10:20pm