They might be referring to using a HDD for a prolonged time at a high temperature probably due to insufficent cooling. HDD's (as I know of, I could be wrong) don't have as fine temperature controls as other computer electronics, so they won't slow down or stop even if they are overheating (which is a problem for all components). So if a HDD dies that way... could it be burn-out? shrug
I did have a 200 gig Maxtor that died on me 2 or so years ago. I never figured out why, everytime I booted up, it was unrecognized. so I RMA'ed it, got a new 250 gig hdd, and I've been happy since... motor burnout? PCB board on fire? Regular burn-out? HDD's work in mysterious ways...