I wouldn't be surprised if that's a factor in many of the problems. This phone runs hotter than any other that I've had, so if there's a component like a memory chip that is a little out-of-spec and is sensitive to temperature, that could definitely cause such problems.
I think there are other possibilities, though. For example, I've managed on several occasions to put the phone into what appears to be a catatonic state (nothing responds except for the button LEDs turning on when the screen is touched) while I was running the Firefox browser. In fact, though, it wasn't frozen, just responding incredibly slowly (the busy circle would move maybe one tick every 30-60 seconds, for example). I think it's related to memory usage: the G2x only has 512MB, and in each case I had opened 8+ tabs in the browser. After a few minutes the browser would finish what it was doing and the phone came back to life. I just limit myself to six tabs or fewer and I haven't had that happen again.