Apple has begun clamping down on developers who were allegedly selling their allotted iOS 5 slots to non-developers. Karthick reported that developers have been getting warning letters from Apple notifying them that they had been identified as having sold their slots, and that some of those accounts were subsequently closed.
In addition, Apple reportedly began locking the Unique Device Identifier (UDID) numbers tied to that account, including the slots sold, rendering those iPhones unusable. Karthick has posted a guide for downgrading to iOS 4.3 if that happens to you, which is the only way to re-activate your device.
iOS 5 is tied to a developer NDA, and developers are required to register their UDIDs to install the new OS. The new iPhone operating system is set to be released sometime this fall, and Apple has not yet specified a release date.