So I was just sticking a DKP system into words earlier and got to thinking about the potential shady side of trading bind on pick-up items. Sure it provides a lot more breathing room for any mistakes since you don't have to wait a day for a ticket to go through. On the other hand think of all the shady things you can do if you have friends or fellow conspirators in the raid with you.
For starters in a pick up group you could ask someone to roll with you doubling your chances to winning or more, if they win they just trade the item to you. For DKP systems you could have folks spending their DKP on others as some part of deal on the side.
A lot of this will be prevented by common sense, if you see a warrior rolling on cloth or a mage rolling on plate there is probably something wrong. Still two people that roll on the same gear could do some pretty shifty things and no one would be the wiser.
Even without any such secret alliances there is now the possibility to bribe the winner of an item with gold or some other incentive to let you have the item instead. Perhaps some of this was happening prior by abusing in-game tickets, but I'm sure if you did it often enough there would be some repercussions.
Something to think about...