You can use the trust system to "tag" accounts.
However, that does not prevent scammers from creating new accounts with neutral trust value.

There are accounts here with very negative trust values, I'd guess that many of them are not outright scammers but either folks whose business ideas were not working out and who burned other people's money, or people who got involved into a dispute with someone who then gave them a "spite" trust rating. Of course some of those with negative trust might be true scammers...

Onkel Paul