It appears that Mabsark is abusing the trust system, but you ended up leaving his positive trust and adding someone to your trust list who previously gave him positive trust.

Having a large trust list does not do anything to stop scams unless they are actually able to use good judgment in spotting potential scams. Even if you were to ignore this fact, the majority of the people on your trust list have only given feedback to you, if anyone.

The result of your trust list is that you have what is essentially a circle of people who have given positive feedback to each-other who all appear to make themselves look trustworthy when they probably are not. This results in people being able to scam by having a somewhat legitimate reason to avoid using escrow for potential deals.

A large trust list also makes it very easy to "cry" scam in order to strong-arm someone to do what they want. Even if people are not abusing the trust system it will result in a lot of false scam reports when someone does not understand how to use the trust system.