I've added users I've done deals with to my list along with some others that I'd trust. I've tagged scumbag account dealers and excluded others who I wouldn't trust with a ten cent loan. I have a hatd time trusting people just because others do. That's my 2 cents.
Edit: this is a good topic IMO, and it shows you care about the forum. My guess is that this thread won't draw in the shitposters who only exist here to make money, who don't read, and don't give a shit about the trust system or this forum.
I'll need to test this out, but does excluding a user from your trust list do anything for the people who have you on their trust list? It would be cool to not only share their trusted people, but also their excluded people. I'm not sure how it works with conflicting entries, though.
EDIT - I've had you on my trust list for a while, and I can only see the people you've trusted in hierarchical view. So I guess it doesn't transfer over.