DT name does not correspond essentially and almost nothing to do with trust.
Maybe not with trust in them in a monetarian way, but certainly with trust in their opinion/decissions and the feedbacks they give.It's not so much about 100% trusting "their" feedback. If the trust rating is factual, with a proper reference (i.e. verifiable) you just need to decide if you agree with "their" reasoning and if the presented facts merit the big red warning.
I probably wouldn't trust 80% of my trust network with any non-dust amounts of money since I have no good way to determine what's their threshold for scamming. But I'm fine with the trust ratings they're posting thus they're in my trust network.
One example is master-P, as he generally did not piss anyone off, so people were not scrietizing his trust ratings, and he was able to give positive ratings to a number of his alts.
DT - or ideally the trust tree customized to everyone's preferences - is just a shortcut to separate the wheat from the chaff but it's not a replacement for due diligence. I can make my network tiny and include only people I trust but that wouldn't be very useful. I prefer a larger network of people whose criteria of evaluating others seems reasonable to me. That doesn't mean I'd trade blindly with anyone who's green on my screen and I wish newbies were somehow forced to learn that lesson before they post or PM in this forum.
There is always going to be a long con possibility in any system if that's what you're getting at, and yes, sometimes a prick like Master-P will sell out for 10 BTC. I think this specific type of escrow scam could have happened with or without a trust system and/or DT.
