billions

The figures are enough to make your head spin: in the first half of 2011 Facebook revealed it had doubled revenue to $1.6 billion - with $500 million of that pure profit - and is on track to exceed $4 billion by the end of the year. Not bad for what began as an online college yearbook.

Facebook's astonishing growth in revenue is closely tied to user growth. The network has accrued a greater number of users than ever before, rising to over 800 million worldwide, extending to diverse demographics and locales, and enabling advertisers to reach and engage consumers with utmost precision and frequency.