I have had "veteran" members with great i-trader feedback back out or not pay up. I have given out neutrals to a few people and one person I let it pass because he is such a well respected member. I go into group breaks now expecting one or two to drop out so I plan accordingly and try to get as many back ups as possible.
Nobody is making me do them, so I figure it's on me to run it as smoothly as I can.
What bugs me most is when people have time limits on draft breaks and they don't pick or communicate at all about what they would want. If nothing else, all I would want is a quick pm stating "hey, I don't care about this break since I got a bad slot. Autopick me what you want." That is the reason I'm going to lay off the draft breaks and stick with either random hit breaks or team breaks.