Here's the deal on OEM. OEM drives are often sold by the manufactuer with no warranty. Then th retailer adds the warranty to the drive themselves, which means that the warranty is only as good as the retailer who stands behind it.
This can be a good deal, or bad deal depending on who you buy it from.
If I buy a regular drive and it breaks, and the guy I bought it from is no longer in business, I have the option of sending it right back to the manufactuer for replacement.
However, if its an OEM drive, I contact the manufactuer and they will tell me to take it back where I bought it...And if they are out of biz, then I'm out of luck.
That said, I buy OEM drives all the time. Some times its a roll of the dice, but the price break is worth it.