I think your disgust might be somewhat misplaced. Looking at the realtime availability map, there haven't been that many tickets sold. I suspect that a huge majority of the tickets that look like they were sold were never released to begin with. Keep in mind that the first 10-15 rows never go onsale at all, even to the people with the presale password. And when you ask why DT allows such a practice, they're one of the culprits. They're holding back 50 or so seats for the VIP package deals, plus a handful for friends/family/associates. The nature of ticket sales nowadays is that great seats are worth more than average seats, and while the scalpers used to be the only ones to take advantage of that, now everybody gets in on the action; including the band. When I suggested that you had to know who to blow, that list includes the promoters, the band's management/label, the venue, AMEX CSRs, radio station guys, and John Petrucci, as well.
Interestingly, this has always gone on, just not to this degree and also some bands are more scrupulous than others. I have contacts with an aging British rock band, and when they come to town I can occasionally get tickets/passes. A while back when they came through I asked my amigo for seats and he had an interesting answer. He said it looked like the show might sell out, and he therefore couldn't give me tickets. The band's policy was that if the show sold out, all the unused holds would back to the pool so the public could get a shot at them. If there are fans who wish to buy tickets but can't, it's better to make more available for them than to just give them to business execs. Thankfully, the show didn't sell out and I had 2nd row seats waiting for me at will call.