Re: My Feeling:
Largely this. My HDD failure rates have always been pretty low. I had a Deathstar fail (but then, I had 3 of them, so I was pushing my luck). I've had a single Samsung drive fail. My home server currently runs WD Caviar Green 3TB, and I've lost 2 of them, I think. But that lives in the attic, so it gets cold-cold in winter and hot in summer. Not the best environment.
I think all the manufacturers are pretty interchangeable for the most part.