Here's a cool chart from The Economist that appears to show that Facebook has a market capitalization per employee that's absolutely through the roof:
But of course you have to think about what business Facebook is in. Their IPO filing confirms that they're essentially in the business of advertiser supported media, not too different from Slate or The New York Times. People spend time on Facebook because they want to engage with the content, and advertisers pay Facebook money because they want to reach the readers. The real workforce of Facebook is all the people who are creating Facebook content. That's closer to 800 million people (roughly their user base) than to 3,000 people (roughly their number of employees). There's nothing new about medica companies getting people to produce content for free (that's what the letters to the editor page or comments section is) but Facebook has built the most amazing vehicle for the appropriation of surplus value that the world has ever known. Ergo its stunning profits and amazing ratio of market capitalization to formal employees.