Revenues and profits
Some interesting things about Facebook that are missing from the article and confound the vast majority of snide comments here:
1) Facebook has nearly double the profits of Amazon in 2011
2) Facebook revenue and profit are both about 1/10th that of Google
3) Facebook has more profit than Google had revenue when they went public.
Raw data in the S-1 filing. Comparison with Amazon and Google courtesy of MG Siegler (http://parislemon.com/post/16888592105/fathoming-facebook)
Now I can't begin to understand where this money comes from but unless they're lying on their S-1, comes it does. You can speculate all you like about user engagement numbers but cash is cash.