These things are largely anecdotal, but one place you can get a sem-scientific idea of how reliable various brands and models (the model can make a HUGE difference) really are: The Reliability Survey over at
StorageReview. There's a very large number of drives entered in there, categorized by model, and the statistics are a combination of the drives still running and how long the drives that failed lasted.
It's a little hard to actually get to the stats, but if you log in and click the "Reliability Ratings and Result Browser" button down toward the bottom, there are lots of interesting statistics to be had. And don't forget to look at a company's more recent products--things change a lot over time.
Examples: the infamous IBM DeathStar drives of a few years back (the 75GXP being the worst of them--had one die abruptly myself) are in fact horribly unreliable, but most recent Hitachi (formerly IBM) drives are pretty good. Maxtors used to be ok, but have been sliding steadily downhill. WD drives are sort of all over, but their newer ones are looking pretty poor (ratings are obviously more accurate after a year or so, since that balances out the out-of-box failures, but the new 2500JB is the worst in the survey, and the new Raptors are very bad as well)
Seagate drives are consistently quite high, and the odd-man-out Samsung is pretty much middle of the road.
This, interestingly, more or less bears out my personal experience gained from running about about 20 office computers and a couple of home machines; I've had very good luck with Seagates and newer Hitachi drives, and all the Samsung drives I've installed over the past several years are still running, but Maxtors have been crappy (sadly, the 250GB drive that Apple put in my G5 is one, which I can't bring myself to use as a primary drive), and I've seen a lot of WD failures.
At this point, I only buy Hitachi, Seagate, and Samsung, depending on wether speed, reliability, or price is the most important (in that order). I'm drooling over the speed on the new 300GB 16MB buffer Maxtors and the 74GB Raptors speed wise, but I just don't trust either for reliability. Maybe in a RAID1 or 5 array...