A member can easily just tag a lot of scammy accounts and work their way up to DT in order to pull off a really big scam.
well but that's the case with everyone else, some people trade with DT members just to get positive feedback "trust farming" and you can see many examples of feedback from DT members even for small deals.
escrow agents may also plan a large exist "scam" , people with higher ranks can also use their rank to scam , The risk is there in every corner of the internet.
besides, you do not need to trust a member to trust their feedback, when you buy something of amazon or ebay and you check the feedback, you don't need to trust the reviewers, I trust many people's feedback but probably only 1 or 2 of them with money, and i am sure that's the case with everyone else. so trust and feedback should really be treated separately IMO.
so if a newbie or member rank gets into DT and spend time and effort tagging scammers,and proves himself to be a good DT member, it does not mean one should trust him with money, that's a whole different subject.