".. After today, Mubarak cannot trust his central security forces ..."

"... It's too early to say that these are "massive" protests -- there are, after all, some 80 million people in Egypt, and no report I've seen thus far puts today's number at more than 100,000 -- but they could easily grow into something truly huge. So far, the police have mostly taken a hands-off approach, albeit with beatings, tear gas, and water cannons in some places. But if the demonstrations continue to grow, Mubarak could face the same dilemma that faced Zine el-Abidine Ben Ali in Tunisia: Crack down for real, try to meet the protesters' demands halfway (say, by sacking his widely reviled interior minister, Habib al-Adly), or some combination of the two.
After today, Mubarak can't have great confidence in his Central Security Forces -- the riot police charged with putting down demonstrations. These are usually slim, scared-looking lads from upper Egypt, poorly trained and uneducated, with little pay and few perks. I've seen multiple reports of the CSF being outmaneuved and backing down in the face of protesters. The army is another matter -- more than a million men at arms, well-equipped and presumably well motivated to protect their significant interests across the country. (He can also call on the regular police and the vast resources of state security, which will no doubt be hunting down organizers in the days to come.) Will we be seeing tanks in the streets this spring?..."