If not there, other sites have noted this was during the huge flood period that happened in the area where the drives are made, the idea being that drives junked by flood were cleaned and still sold. Don't know if that was the truth, but considering how the failed drives manufacture date line up with the flood dates, I wouldn't put it past them.
Here's the lie they put out in 2009, but never backed up.
About those floods.
"Thailand is the world's second-largest producer of hard disk drives accounting for approximately 25% of the world's production.Many of the factories that made hard disk drives were flooded, including Western Digital's, leading some industry analysts to predict future worldwide shortages of hard disk drives.Western Digital was able to get one of their plants, flooded on 15 October 2011, back up and running on 30 November 2011. Western Digital's flood-related costs were estimated at between US$225–$275 million, however, an insurance claim of US$50 million for property damage, and another claim for business interruption will help lower the net impact.As a result, most hard disk drive prices almost doubled all over the world, and then slowly started to come down."
Surprisingly, Seagate itself wasn't affected as badly by the floods, but some suppliers of their components were, and that may be where their problem came from, whereas Western Digital who was hit, having tighter control over their components dumped their damaged stock. So, where did the failure actually happen? Was it flood related? Some firmware problem like WD had with it's "Green" Drives? Can't say for certain, but seems more related to the actual storage media itself perhaps, the coated platters used in the drives.