The 'nerds' (computer-savvy persons) tell us that laptops are now supposed to be called 'notebooks' and say that they should never be used on soft surfaces because blocking the vents may well ruin the computer. I did not know this until reading Ditter43's warning and checking Snopes.com. Thanks, Ditter.
Apparently faulty batteries are more likely to cause computer fires (HP has done recalls because of this).