You're not alone. I am in the UK and it's happened to my S3 three times now. I had a suspicion that it was related to the device either spontaneously resetting, or getting to a state where it had to be reset (hold the power button for several seconds). The last time it happened was, indeed, after it had reset (when I picked it up it was just rebooting and I noticed that I wasn't receiving email a couple of hours later).
Anyway, I think that is what's doing it and, although I had hoped the latest firmware update may have fixed it, it hasn't.
Luckily, it doesn't take too long to recreate the accounts and I'm sure that Samsung will eventually recognise the issue and put a fix in place.
It would be interesting to know if any other ICS-equipped devices have a similar issue. I'm thinking of the HTC One and the latest Sony Experia devices.
Good luck...