I agree that part of the issue is that most of them do have self esteem issues. My problem with that several of them were fans of BB and didn't take the time to think about the usual dynamics in play before coming into the house.
I call it the Jason effect because of the current group he's the only one with practical experience in what it would be like going into the house, yet it appears he didn't learn anything from his last go around. Allowing yourself to only interact positively with your clique and reinforcing the us vs them status only solidifies the core members of the alliances and prevents them from recovering if the other side goes on a power streak. This is normally a bad position when you have the popular/social crowd vs the jocks but this season when you have America voting, well it could easily become terminal. While America likes to root for the underdogs, we like our underdogs to at least act somewhat respectful to the others and grateful for our help. Jason & crew have acted like America has to support them, uh no we don't.