Does Facebook want their service to be used by Egyptians to overthrow their government? Probably not. They're trying to get China to let them in.
Chinese Internet censors don't want the people to hear about Egypt.
Zuckerberg went to China, very visibly. Google has been there, and withdrawn, and now would probably like to go back.
When people think of the revolution in Egypt happening on Facebook and Twitter, what they really need to know is that these two corporate-owned websites are part of the Internet. It is that part that is useful to revolutionaries. The corporate side of their existence is an opposing force, because the tug of governments and profits makes them want their services to not be used for revolution.
BTW, this is something the VC community can agree with, imho. The evolution of social media to the edges will just create opportunities for new products, new startups, more money. As Bruce Sterling says, we're always centralizing then decentralizing then centralizing. It's the pulse of tech.