This is a typical illustration of why only developers should install a beta version of a software. In this case, I'm specifically talking about iOS 7 beta, which has been wildly popular among non developers since Apple first made it available in June.
Of course, we've tried to warn everyone that unless you're a developer, you shouldn't really mess with iOS 7 beta. Since yesterday, those that didn't take this warning seriously might have gotten themselves into trouble.
iOS 7 beta 6 was set to expire on October 6, and people who haven't updated to the GM or public release by then found out the hard way that a developer release should really be only for developers.
Many people were greeted today with a message on their iOS device saying "Activation Error - This device is not registered as part of the iPhone Developer Program," rendering the device unusable. Activation Required...