What Facebook Knows

If Facebook were a country, a conceit that founder Mark Zuckerberg has entertained in public, its 900 million members would make it the third largest in the world. It would far outstrip any regime past or present in how intimately it records the lives of its citizens. Private conversations, family photos, and records of road trips, births, marriages, and deaths all stream into the company's servers and lodge there.

Facebook has collected the most extensive data set ever assembled on human social behavior. Some of your personal information is probably part of it. And yet, even as Facebook has embedded itself into modern life, it hasn't actually done that much with what it knows about us. Now that the company has gone public, the pressure to develop new sources of profit is likely to force it to do more with its hoard of information. That stash of data looms like an oversize shadow over what today is a modest online advertising business, worrying privacy-conscious Web users (see "Few Privacy Regulations Inhibit Facebook") and rivals such as Google. Everyone has a feeling that this unprecedented resource will yield something big, but nobody knows quite what.