The Egyptian government cut the cord on the internet to silence them form the outside world, keep protesters from organizing, and generally, to shut them up:
Now Internet access across the whole nation has been shut off, as the Net traffic volume chart from Arbor Networks embedded here shows. As an investigation by Renesys demonstrates, at around 12:34 in the morning local time “virtually simultaneous withdrawal” of all Egypt’s networks connected to the world’s IP routing system—meaning data access routes into or out of Egypt were shut down. It’s a complete order of magnitude more severe censorship that happened in Iran, when the government tinkered with blocking social media sites, and is far worse than the “modest Internet manipulation” that the Tunisian authorities tried as similar protests happened there. Essentially the Egyptian government has realized it cannot stay one digital step ahead of its population, and has simply thrown the off-switch.
It’s unconfirmed, but they may have also blocked Al Jazeera within the country and even journalists are being attacked in the streets. But this hasn’t stopped Egyptians; according to The Guardian, they’ve started distributing literature on the street, old-school-revolution style.