I'd be shocked if it were hardware. That said, I'm guessing it has to do with the network stack, specifically with regards to cellular data. I don't think it's a problem with any particular app, given that it appears that people have had the issue regardless of what apps they have had installed.
I can't think of anything else that would be that random and, yet, predictable. It's always the same result (a reboot), just at unpredictable times. It's never a freeze or anything else; it's always what appears to be a kernel panic.
I wish we had an Event Viewer on these things.