Every drive manufacturer has a bad batch once it a while, sometimes even a bad design for one drive. IBM had this problem with their first 7200 RPM drives, Most companies recover from the situation, I'm suprised WD did not. Maybe your just unlucky?
Wow, I've had a couple of WD Caviars for a few years and they've been running without any problems.. I had one in my server on 24/7 and it ran without problems. I only recently swapped it out for cheaper Maxtor drive.