Today's Facebook IPO makes it clear how valuable each user is to the company ($115.43 if you wondered), and with a reputed 800 million active users it can seem hard to find people that aren't members of the site.  A common explanation for those few that aren't on the site is that they object to putting all of their personal information onto a site and for that site to then make money off of selling that information to advertisers.

Alas some German researchers have managed to find out heaps about such people even though they're not on Facebook.  The researchers managed to paint a pretty good picture of those that abstained from Facebook just by monitoring the postings of their friends on the site.

The researchers looked at publicly available information on Facebook to determine with an "astonishing" rate of accuracy whether two non-members knew each other based on information posted by their friends.

People worried about revealing details about their lives, political views, or other sensitive information online often stay away from social network platforms "in the belief that will help protect their privacy," the researchers wrote in the paper's introduction.

"Such an assumption is no longer valid," they concluded.

And that's the problem.  Even if you're not a member of Facebook yourself there's still a reasonable chance that your friends will be, and they will post things about you on the site.  For instance you may be snapped at a party, with the photos uploaded by a friend or they could check into a location and mentioning they're on holiday with you.

If you were so inclined you could gain a good understanding of someone just by spying on what their friends make available in the public domain.

A Carnegie Mellon researcher demonstrated at last year's Black Hat conference how he was able to apply off-the-shelf facial-recognition software to Facebook photos to identify 30 percent of students walking around CMU campus. Alessandro Acquisiti took his research another step further and correlated the publicly available information with anonymous profiles on online dating sites. He was also able to correctly guess Social Security numbers within four tries for 28 percent of the subjects. And all this started with just a single photo.

So, it would seem, the only escape from the clutches of Facebook is to have an entire circle of friends that don't go near the place.