MacBook random shutdown: balky heat sink sensor

I'd read many theories about the random shutdown problem with MacBooks. None of them turned out to be right. Apple had a hard time sorting it out -- they were replacing motherboards and machines for a while. The problem, apparently, was in a heat sink sensor:

PC World's Techlog MacBook Shutdowns: Case (Finally) Closed?

... Last Monday: I get a phone call; my system is ready for pickup. The courteous Genius who gives it back to me provides more details on the defect: Some MacBooks have a heat sink sensor that malfunctions, thinks the system is overheating when it isn't, and shuts down the machine thinking it's preventing potential damage.

Modern laptops are insanely complex. Apple needs to invest more in self-diagnosing hardware.