Hmmm. This would be neat, but easily abused. Who can edit it? Scammers could easily put false accusations against someone else. The trust system at bitcointalk is enough in my opinion.
I had the same idea myself, I lost 2 BTC to an add here in the forums for mining hardware. People are now buying/selling bitcointalk accounts, so even that has become an issue. You're right though, someone could just abuse the system and enter in false accusations.
New entries could be listed as with a transaction hash as a required field as part of some proof of a transaction. Another option would be the capability to vote up and vote down an entry with a cooling period so that someone wouldn't just register accounts and quickly vote-up, vote-down an entry. Entries could be marked as "suspect" on some sort of trust meter too until some type of admin-based validation is done. An example would be where the community continued to warn on lunamine as a scam, then they really turned out to be a scam when they up and left.
Good idea though, just needs some more features I think
