I think I've had it happen once over something like a decade of using them. From what I remember it was because I was running something in the terminal that ignored the signals it was sent, so the laptop didn't properly go to sleep. Of course, the program ended up failing because a lot of the things it depended on did suspend themselves and that caused major breakage.

Luckily I noticed a whining sound (fans at maximum speed) from my backpack before anything too bad happened.