I have seen cases of DT member being removed because they are giving negative feedback in a way that is not proper.
Read this comment from theymos.
However, I reserve the right to remove you and blacklist you from future selection if you engage in egregious and obvious abuse, or if multiple known alt accounts could be selected.
A DT member is not suppose to give someone negative feedback without good evidence or attaching it with reference, I see a lot of people giving negative feedback and no reference, this is one thing that is reducing the value of the DT and trust system.
Something of this such might have happened in the past which I may not be aware, since am still new to the forum just a year plus. But through out my stay here in the forum I don't think if I have seen any case where a DT member gave another user negative feedback without good evidence or without attaching a reference link.
All the negative feedback I have seen so far from DT members is accurate. Although some DT members still abuse their DT power, because I have seen cases where a DT member gave negative feedback to another DT member and the DT member retaliated by giving the user the same negative feedback .
However, DT members shouldn't give negative feedback out of speculation, and they shouldn't also give negative feedback to users, just because they are feeling suspicious towards them. If a DT member is feeling suspicious towards any user or group of users, he or she should create a thread for them, so that the users would be investigated. And if they are find guilty they should face the consequences.