These drives are low performers, and by all account here they don't compensate with reliability (as of writing 12.5% of Amazon reviewers reporting failed drives). This is different to actual failure rate, and according to behardware the overall return rate of this exact model is 2.31% and that's not bad (great is 1.80% for the Samsung SpinPoint F4 EcoGreen 2TB, disaster is 7.53% for the Seagate Barracuda XT 2TB SATA ).
However I'm not really happy with this purchase and it's destined for an external USB enclosure to store low-value data such as downloads.
If you Google out "wd green parking" you'll see they also have overly aggressive head parking resulting in LLC (Load/Unload Cycles) counts that can pass MTBF within just a few months.
There is a wdidle3 utility released by the manufacturer that can be used to reduce parking to a more reasonable 120secs (instead of the factory setting of just 8secs) but that's a right pain as it needs to be booted in DOS.
For the curious, here are the manufacturer return rate overall for hard drives:
Do bear in mind that each manufacturer is still liable to produce a really bad model with nearly 10% return rates. You need to Google the exact model number (e.g. WD20EARX) in your research to avoid these.