On other forums with this kind of thing has actually worked out quite well when moderated correctly, at least in terms of making fraud, etc. demonstrable to new people. It can get out of hand and become a kind of blind crusading though.
There have been a few martial arts forums that implemented a (very well moderated) sub forum for fraud and abuse that have ended up directly being used as a resource in a positive way. I assume the key is good rules for moderation. usualy what happens though is the aggrieved party shows up to "defend" themselves online, and often in the process it's easy for people to suss out where they stand. I don't think it's a bad suggestion if it can be moderated well.
The more you do stuff like this though, the more it requires transparency on the part of users and moderators, things like asking people to use real names etc...I imagine it's harder to moderate with a more transient and anonymous user base.
"Just as a lotus does not grow out of a well-levelled soil but from the mire, in the same way the awakening mind
is not born in the hearts of disciples in whom the moisture of attachment has dried up. It grows instead in the hearts of ordinary sentient beings who possess in full the fetters of bondage." -Se Chilbu Choki Gyaltsen