I think almost everyone carries a laptop in a bag, and most don't have ventilation. The problem was that even though my linux configs were set (correctly) to sleep when closing the lid, it would often get prevented from sleeping by a program or driver that didn't respond properly to the sleep request. I did mention the case where Windows had a similar issue.

I was only trying to show that the OS and Software can play a big role in the health of the hardware. Software bugs can cause hardware failure, and a notebook not going to sleep when the lid is closed is usually a bug unless it is specifically configured to do that.