This is starting to look like Tehran the summer-before-last. Your guess about what this means is as good as mine. That the thugs are organized doesn’t mean that Mubarak or his henchmen are doing the organizing as a means of retaining power. It could just be that reactionary elements are mobilizing to win themselves a seat at the table at which the parameters of the new regime will be negotiated. But it’s a pretty good sign that, however it turns out, Egyptian regime-change isn't going to look much like the velvet revolutions in Eastern Europe.“[T]he pro-Mubarak thugs are arriving in buses and are armed — and they’re using their weapons.
“In my area of Tahrir, the thugs were armed with machetes, straight razors, clubs and stones. And they all had the same chants, the same slogans and the same hostility to journalists. They clearly had been organized and briefed. So the idea that this is some spontaneous outpouring of pro-Mubarak supporters, both in Cairo and in Alexandria, who happen to end up clashing with other side — that is preposterous. It’s difficult to know what is happening, and I’m only one observer, but to me these seem to be organized thugs sent in to crack heads, chase out journalists, intimidate the pro-democracy forces and perhaps create a pretext for an even harsher crackdown.”
Update: Here's a more informative post from Graeme Wood about the conduct of pro-Mubarak thugs.