I think that rebellion for the sake of it can be very useful as it leads one to push the boundaries and explore new avenues. Obviously it can sometimes go tits-up but that's the risk with this sort of thing.
However I must say that rebellion in the form of the likes of the occupy movement make me cringe a bit. The trouble is that they're attempting to change the world but have, or appear not to want, any genuine alternative to the current situation so it all ends up looking a bit pathetic. They seem to think that some form of spontaneous utopia will spring out of the ground like some sort of anti-capitalist beanstalk.