The early acceptance and rejection letters are arriving to developers who applied for the iPhone Developer Program ($99/year). More rejection than acceptance it seems. Many developers received the following non-acceptance email from Apple:
Dear Registered iPhone Developer,
Thank you for expressing interest in the iPhone Developer Program. We have received your enrollment request. As this time, the iPhone Developer Program is available to a limited number of developers and we plan to expand during the beta period. We will contact you again regarding your enrollment status at the appropriate time.
Thank you for applying.
iPhone Developer Program
The $99/year iPhone Developer program comes with the beta iPhone Firmware and allows developers to install their applications onto the iPhone itself, rather than just onto the emulator. Apple is expected to open up the program to all comers after June, but in the meanwhile is only open to a "limited" number of developers.
Update: Despite some circulating theories, not every developer who has applied has been "rejected". Besides, this limited acceptance is only during the "beta" period which lasts until June. Past that, it's believed that all applicants will be accepted.