Maybe I'm cynical, but I believe that the VAST majority of people are already unhappy with their jobs. In fact, the vast majority of people have been unhappy with their jobs for hundreds of years - probably thousands. They don't do them because they are happy to work. They do them because they want to eat.
Is there some kind of breaking point? There is for everyone, but I don't think satisfaction is the red line. For most people it has historically been things like pay and health and safety. If everyone were to suddenly have their pay cut in half, I could see that resulting in general unrest.