Funny story, I was moving back to the US after living in Japan for 4 years. Moved out of my house and was staying with a few friends for a span of about 3 weeks before heading back stateside. In the midst of this, one day my Macbook Pro simply froze. I'm used to clocking my machine's ram until things can slow to a crawl, and figured simply it was time to for a bi-monthly (or so) restart. But the machine never booted after that, and I got the question mark of death. I had been lazy about my Time Machine backups, and thought I'd for sure lost all my data. I decided I'd worry about it when I got home.
Right after landing, I decided to cut my losses and ordered a new hard drive (upgraded from 500 gb to 750gb) . However, after installing, the brand new hard drive did not boot, which REALLY made me worry. But I was pleasantly surprised to see that my old hard drive booted externally, meaning it was not a hard drive issue after all, but most likely a problem with the cable.
I was comfortable with installing a hard drive, but had never installed a hard drive cable before (much less in a MBP), so I was really apprehensive about doing this. Still, I ordered it from iFixit and followed the instructions. It was really not so bad, and in around 20 minutes everything was in and I started the machine and crossed my fingers. FIXED!! (Sorry, I forgot to take pictures)
For this who encounter what they believe is a hard drive failure, you should really check to see if that's actually the problem and NOT the hard drive cable. I ended up getting a brand new hard drive that wasn't required, though as I had been planning to upgrade anyway, this was not a problem for me. I placed the old one in an enclosure case and now use it for time machine backups!