Of vacuums and regime changes

Regime change is a many sided thing.  The biggest problem with it is what happens when you take the existing leader out.  In Egypt, there was the structure of government, assured by the military, that allows for some sense of transition including elections, we hope free.  In countries like England and Australia a government may fall, but the opposition operates a shadow government that is ready to step in.  When the Shah fell in Iran there was a government, however repressive that was ready to go.  In the first Gulf War one of the reasons we did not take Hussein out was there was not one to replace him.  We did not heed that in the second Gulf War.  In Libya, who will take the place of the current dictator?  There is no government in exile ready step in.  We do not even now who to talk to among the rebel forces.  A vacuum created like this is most apt to be filled with someone more repressive or just with ongoing civil war