Hmm, its curious. I am pretty good at coming up with examples or picking out items from crowded environments. Well, for the social changes... what's about gradual abolition of religious fundamentalism? It can be self enforcing (just as introduction of fundamentalism is; instability implies self-enforcing effects both ways).

In general if you can come up with some self-reinforcing social change that you think is bad, the same change, starting from the bad state (assuming that it can start at all), would be self-reinforcing in the good direction. A steel object falling off from under a magnet is a self-reinforcing process - the further it falls, the lower is the attraction - and so is the steel object snapping onto a magnet - the closer it gets, the stronger is the attraction force.

edit: ahh, i looked up in comment thread. Indeed, the problem is that it is hard to keep unstable process in equilibrium, and the self-reinforcing processes go too far. At same time, if you take a terribly religious population where we burned witches, or where they stone the rape victims to death, it is easy to imagine that on the other end of the slippery slope - if the slope is at all inclined in the other direction - the life is massively better.

I made a magnetic levitation device once - it would suspend iron nail under electromagnet. It seems deceptively simple - when nail goes up, turn off magnet, when nail goes down, turn it on - but if you do so you get rapidly increasing oscillations - you have to have a circuit that blends in first and second derivatives of the position into the control signal. A great deal of complexity for a very simple unstable system.