Crap HDD's... Bad Quality Control?

Hi! I am new here.

I have been dealing with some crap lately, and I thought I would get the input of some other geeks

I own an IT business, computer repair, computer networking, etc...

I have been having a major problem with brand new components, mostly with HDD's. Lately I would say that 1 out of every 10 HDD's ends up being a DOA or failing after 3 months. Has anyone else seen this kind of behavior from new HDD's? The drives I primarily use are the WD Caviar Black, Caviar Blue, Caviar Green, and Seagate Barracuda.

I don't know what the hell is happening!:mad These are supposed to be top quality drives. Has WD and Seagate gone down hill? If so, does anyone recommend another manufacture?

Thanks for the input!!