Yep, I don't doubt that for one second--but Theymos generally keeps his hands off of the DT membership and their behavior.  If a DT member is leaving feedbacks like those, it's kind of up to other DTs to exclude the person who's leaving wrong negatives like those. 

And yes, it is a very imperfect system and there has been a lot of misuse of it and that probably won't stop completely, since anyone can leave feedback for anyone else and trust isn't moderated.  Hopefully DT members are doing the best they can to clean their own house, so to speak.  That's how it's always worked (and sometimes it doesn't work very well).