It might be a faulty assumption that something needs to be done.

Trust no one. Learn personal responsibility. #bitcoin is going to make this imperative because you can't rely on a central authority fixing it for you.

If you have a central system for tagging scammers the scammers will find a way around it. The marks will trust people who aren't tagged. You've only created a way for the scammer to get free credibility. Look at what happened when verification on Twitter became $8 as an example of this playing out.