My friend and I were sitting at lunch today, both with iPhone 5 and iOS7 chatting about how we like it. I thought I would try Airdrop (never used it previously). I went to send him a picture I had just taken with my iPhone 10 minutes earlier. It showed FAILED on my phone, and his phone started vibrating and then completely locked up, stuck on vibrate. He powered down and back up and we tried it again. This time he got the picture, and when I looked down to my iPhone, it was rebooting, too. What's the deal with that? Two unrelated iPhones both going haywire with Airdrop?