At the end of June, nearly 1.5 billion people used Facebook (FB, Tech30) at least once a month, the company reported on Wednesday. That's more than any other technology product in the world, including Microsoft's (MSFT, Tech30) ubiquitous Windows operating system. This tremendous size has allowed Facebook to build a ton of new features that capitalize on all the data it has on its users -- primarily by selling targeted ads. During the second quarter, Facebook's ad sales topped $3.8 billion, 43% growth from a year ago. The success story was even bigger for Facebook's mobile ad business, where revenue rose 62% to $2.9 billion. That is an impressive number considering none of its sales came from phones as recently as three years ago.
