Duke University reports that they're losing communications with several of their wireless network's APs, all of which are in the same general local. After some initial troubleshooting, the staff has decided the problem is due to an unusual quirk of the iPhone.It appears that the iPhone is broadcasting MAC address requests at a rate of 18,000 per second, which has the potential to overload all of the APs within range of the iPhone. Apparently the iPhone is requesting the MAC address of the last known gateway device whose IP address it has stored. If the contacted AP is unable to resolve the address, it will not respond. The iPhone then continues to send requests for the MAC address creating the DoS situation. If the iPhone moves out of an affected AP's coverage area, the AP almost immediately returns to normal operation.
Duke University is using Cisco equipment and has opened help tickets with both Cisco and Apple. Also they are interested in learning if any other universities or large scale wireless networks are experiencing similar circumstances.
For more details, you can refer to this NetworkWorld article.