Reaction #2: "assuming Facebook's earnings are anywhere near their height is like saying 'OK, so you conquered the entire world and every army is prostrate at your feet, but you haven't looted any treasuries YET, so the whole thing was clearly a bust.'"
Reaction #3: "CBS is valued at 30 billion dollars. It was probably worth a lot more in 1985 although I can't seem to find a figure. Facebook is saying they are worth 100 billion dollars. They have one billion users, and they know WAY WAY WAY more about those users than CBS does, and they can market to them individually. 100 billion is about right for Facebook."
Reaction #4: "the usefulness of a social network is a function of the percentage of your peeps who are on it, becoming asymptotic as it approaches 100%. Everybody is on Facebook, therefore nobody will ever join a Facebook competitor, even if they would like to. They are only going to get bigger."
Reaction #5: "I encouraged friends to try an alternative social network. They replied that they did not know the email addresses of their friends and so could not invite them. Facebook is worth at least $100 billion."
Reaction #6: "Google is valued at $200 billion. Their business is also based on contextual advertising, and they know less about their users in some ways than Facebook does. They have tried and failed to unseat Facebook in social networking. Facebook is probably worth at least half a Google."