Facebook is possibly the worst bubble in history. It should be worth 1/20 of what it is today, or less. Like Bitcoin, it's mostly a 'virtual' thing with little underlying assets and it's value is driven entirely by the popularity to its userbase. Once it loses that popularity, it can simply collapse to nothing, like Myspace. Facebook has absolutely no business being half of the market cap of Google, which has 1,000 times more code and useful applications than Facebook.