Default trust doesn't give anyone on it an "advantage" its a huge responsibility. Being on the default trust list means you give others appropriate feedback, it doesnt mean that you are without a doubt trustworthy. How trustworthy someone is should be a huge consideration when adding someone to the default trust list, but its about who you can trust to leave accurate feedback for others.

If I add someone to my trust list who is a jackwagon, its my responsibility. That sure is a pretty good motivator not to mess up the default trust list. If I add someone to my trust list who I don't have complete faith in, and they add someone who is a jerk, once again I'm held responsible. I'm not going to stake my own reputation so a friend of a friend of a friend can go on a perceived power trip. They get cut, and the system corrects itself.

If you want a system without default trust, all you have to do is look at "untrusted" and "trusted" feedback with the same weight. I don't give trusted feedback any weight unless its from personally someone I trust. If I see Badbear is trusted by Dingus, Doofus, and Dingleoid and I dont trust them even though they are on the default trust list, I dont value their feedback anymore than untrusted feedback. If Badbear is trusted by someone I trust default trustlist or not, that carries the most amount of weight.