Two thoughts on Egypt

1. The first historical comparison that came to my mind was 1848, but I've seen at least one writer compare the street protests to 1989 in Eastern Europe. The revolutions of 1848 were related but separate, and they mostly failed, or were undermined soon after... but the people remembered, and eventually democracy won (more or less). 1989 was the collapse of an empire, with local governments' weakness in the periphery demonstrating the fragility and lack of power of the Soviet Union in the center. If this is 1989, then the empire that is weakening is the United States.
2. If Mubarak goes, quite possibly the Egyptian cooperation with Israel's Gaza blockade will also go; I suspect it's not popular with actual Egyptians. Relations with Israel would deteriorate. Separately, this would increase the chances of Israeli military action in Gaza. Relations between Israel and Egypt would deteriorate further.