Engineers at Google have published a PDF concerning hard drives and what factors are most likely to cause them to fail. They studied 100,000 hard drives over the course of five years and had some pretty interesting findings.
"It is estimated that over 90% of all new information produced in the world is being stored on magnetic media, most of it on hard disk drives. Despite their importance, there is relatively little published work on the failure patterns of disk drives, and the key factors that affect their lifetime. Most available data are either based on extrapolation from accelerated aging experiments or from relatively modest sized field studies."
No names or brands are given in the PDF, but you may (or may not) be surprised to read that specific models and manufacturers are more prone to failure than others.