My 780 overheated, started smoking then died. I have another one and that one is workring just fine and I have a huge case (Coolermaster Striker) with no other cooling issues.
It wasn't making noise or anything just working fine till I started smelling smoke, look down at my computer and saw a little puff of smoke, and it shut itself off. After I took the card out everything worked fine. Also the card that died was on the top with only a 2 SLI setup.