My iphone 4s was running the iOS7 betas. The last update was the GM beta and it never asked to update again (apparently 7.0.2 has been out)?
I was listening to a podcast and the audio was still playing when it locked my screen and demanded activation. Trying to activate, it says "can't connect to servers". Connected to itunes, it says "this software is out of date...". Backup, sync, and restore both give "cannot connect to iphone" messages. I'm currently downloading the 7.0.2 firmware on a 1mbit connection (3 hours to go!) and hoping a DFU boot and alt+restore will work.
Last time I run my podcasts on a device that can disable itself.
Edit: Twitter complaints here:
https://twitter.com/search?q=iphone%20activation&src=typd&f=...
Judging by the amount, I don't think it's a few devs having this problem.
Edit2: Booting to DFU or Recovery mode seems to let you start the restore process. Clicking on restore didn't give the same "can't connect to iphone" error, but oddly said it was going to download 6.1.3 for me. Good sign that alt+restore will work.