There are a lot of people who are on DT who have negative trust. It seems there might be a mismatch between who is on DT and who should be on DT.
Just because someone has received negative "feedback" from someone deemed trustworthy by some users doesn't mean they can't also be trustworthy to other users. This seems to me the system is working as intended and spreading out the Default trust as opposed to having it be a core group.
It should really only be used by newbies anyways as more experienced users should create their own custom trust lists.