An opt-out is a good defense that the companies should have done a long time ago to avoid criticism and getting into this situation in the first place. It's doubtful that too many people would take advantage of it, and the companies can just point and say "see, we allow an opt-out!".

But as a society, I think an opt-out is a poor thing to encourage. If the behaviour is not acceptable, why should people have to opt-out, instead of opting in?