Back when I worked for Maxtor I got to see a few info that explains why some drives fail more than the other:
1) Some drives are mishandled by the vendors and that is the #1 reason they fail in consumer's hand.
2) Within the same brand, some generations are bad because they were falling behind their competitor and was squeezing the last safety margin out of the drives, or testing didn't catch some quirky bug that shows up after a few thousand hours of run.
3) Consumer buying drives from a store always get the non prime units. The prime ones are always sold to the large OEM because they demand even higher quality to avoid costly RMA. Consumer usually are ok even if they lose a drive and send one in for RMA and get a replacement.
4) No drive is guarantee to last forever, backup is a must if the data is important to you.
At the moment if you want to get Seagate, they have a bit of problems with the 11 series that supposed to have been fixed in the latest firmware. WD seems to be ahead in the power consumption, Samsung seems to be ahead in noise, IBM as usual are strong in performance (they have the best command recombine algorithm according to a 15 year veteran that defects to us in SanDisk), and Seagate used to be in reliability (suppose to be until the 11 series).
The rule of thumb is: every drive company messes up once in a while, and their technologies are usually within a few months of each other due to cross licensing / patenting in the industry. So don't buy based on brand, buy based on model.