tl;dr they own a lot of tubes
A Facebook glitch briefly took down a large number of sites that use the social network’s login credentials on Thursday — highlighting just how wide Facebook’s reach has become.The glitch lasted a few minutes and affected only those who were logged into Facebook at the time. But there were widespread reports of users having trouble getting to sites such as Gawker, CNN, Mashable and, yes, The Washington Post. When users tried to visit those sites, they were sent to a Facebook page that displayed an error. To get around the bug, users had to log out of the social network. Facebook released a short statement after the outage, saying, “For a short period of time, there was a bug that redirected people from third party sites integrated with Facebook to Facebook.com. The issue was quickly resolved.”The company has yet to provide further information about the flaw or say how many Web sites may have been affected.While the outage was a short-lived problem with a fairly quick work-around, some sites with Facebook integration may find it troubling that a flaw in Facebook’s code could affect so many users.