When you can prove someone is trust-able then he can get a trust tag or something like that.
Unfortunately, that wouldn't work. Pirate would have had a "trustable" tag.
One thing that people don't do enough is to go through the posting history of the person they're trading with. Recently, BTC Guy was the topic of discussion because he took off with people's money. In going through his posting history, it was obvious (to me, anyway) that I'd never trust the guy with a bag of turds much less a bitcoin.