I feel the main reason that half want to walk, well, apart from 'jumping on the bandwagon' is that they heard Lynne being booed, they may also have heard Lee being booed, and its suddenly dawned on them that when they go out that door there are going to be literally hundreds of people outside. Yes, they're on telly to goodness knows how many viewers, but to them, thats not 'real'. I know if I was in the house right now I'd be terrified of going through that door!!
Also I agree with others, that the precedent has been set so its easy to do now isn't it.