My hard drive failure rate is uhmmm... I never ever ever had a hard drive fail on me, no matter how old it was or how much I grinded the head. Except one drive: A Western Digital Green drive 1.5TB which was used in an external BlacX thingy. So it spent most of its life OFF. It was on for a few hundred hours of very mild use then just gave the CLICK OF DEATH and died. 
funny, only drive i've ever lost is a WD green 500gb, infact I got it working again -accidentally- by smearing some thermal compound on the logic board - maybe it fixed a dodgy via or cold solder joint.
I wouldn't recommend people do this however:D but if there's stuff you need off it, then a replacement logic board might be worth a try.
