updated 09:36 am EDT, Wed June 12, 2013
Still allows cables' use
The iOS 7 beta is popping up a brief warning for people trying to connect unauthorized third-party Lightning cables, various accounts say. "This cable or accessory is not certified and may not work reliably with this iPhone," an example message reads. Notably, though, the cables should indeed work after the warning is dismissed.
Apple's first-party Lightning cables contain authenticator chips. Initially that prevented third parties from competing in the cable market without Apple's approval, but reverse engineering eventually allowed unauthorized cables to work. The main reason to go with an unauthorized cable is cost, since approved ones start at $19 and only increase in price from there.