My hard drive went completely dead about a month ago. I bought my MacBook when they came out about a year and a half ago. I did not purchase applecare so it was no longer covered under warranty. So I had to fork over nearly 300 dollars to get both a new hd and a new optical drive. I've pretty much had nothing but problems with this machine (random shutdown syndrome, bad hd and optical drives, etc.) So in a way im glad Apple is acknowledging these hard drive failures; maybe i'll get some of my money back I just payed to have them repair it. Sorry to complain so much but when I bought my Macbook I was a new switcher and I've been given more than enough reasons to switch back but i've stayed loyal.
Just some tips based on what happened to me about knowing if your hd is going bad (not sure if all these were related to the hd but just to note a few of the things I noticed before it complexly died)...computer would just shut off, no low battery warning or anything, sleep light stopped working, and also screen was flickering from time to time. When it came to dieing, I opened my Macbook to awake it and the screen was frozen, reset it and got nothing but a white screen with a blinking folder with a ? mark.
Good luck to everyone who has these hard drives in their Macbooks, make sure to keep things backed up.