Alinsky is interesting to me because it seems like he was one of the first to notice a new, likely to be effective method of social change - and he used up all the effectiveness of the technique.

I wouldn't expect non-violent protest (in America) to be capable of that kind of social change in the future, because those in power have learned how to deal with it effectively (mass arrest for minor infractions and an absolute refusal to engage in political grandstanding). By this point, mass protests are quite ineffective at creating social change here in the US (consider the relatively pointlessness of the Occupy movement)

I'm sure there are other examples of techniques of social change becoming totally ineffective as authorities learned how to respond better, but I can't think of any off the top of my head.