Thats definitely a really good feature however i never understood the lack of scam moderation either. In the scam section there are plenty of accusations that are already shown to be true beyond reasonable doubt and the scammer accused is still in the forum, yeah he might have red trust, but why isnt he banned? And before you say things like, its hard, it wont help banning him, what about the other bans that are happening, the sig campaign bans for useless posts, how come they have time to moderate that?
If moderators/administrators assumed the responsibility of identifying scammers, then it's quite possible that the community might become more lax and less vigilant about identifying scammers and all of the bannings could potentially create a false sense of security. Those scammers who do pass the staff's checks would then be able to cause even more damage when their ponzi/dice site/exchange/whatever shuts down. Hence the trust system is there so that we can see make our own judgements as to whether or not something is likely to be a scam. Once an account has deep red trust, there is no way that anyone is going to trust them for any further trades so banning them would be unnecessary.
Also, there is a question of who should be banned as well. I won't say any names but there have been people who made a mistake and blew their investors' funds, but later came back and admitted to their mistake and are now active members of the community. Then there are cases like Inputs.io and Mt. Gox where it's not clear what exactly happened. Were they scams? We can't really know for certain.
For a normal forum, it would probably make sense for moderators/administrators to identify and remove likely and confirmed scams. For a community such as this one where a large percentage of all services end up being scams and new ones pop up daily (check out the investor-based games subforum for examples), it would just be too much work.