if facebook manages to earn 100 present value dollars per user per lifetime of their facebook usage on a user base of 600 million, they should be worth 60 billion. It does not seem outrageous at all. Using their average profit per user over the last 5 years, as the article does, seems a bit silly because in the first 4 of those 5 years they were focused on acquiring users, not so much on monetizing their usage.