Happens all the time unfortunately...with other types of hardware as well.
The two above average hard drive experiences I've had are:
1. I ordered a 40 GB HDD for a relative from NewEgg about 5 years ago. In the box came a 40 GB and a 120 GB. The 120 GB wasn't on the invoice and I didn't pay for it. I used it for about 3 years!
2. A couple of years ago I went to best buy to replace that 120 GB hard drive that failed after moving it to another PC. At Best Buy they had a 74 GB 10,000 RPM Raptor there for $115, not on sale. I checked NewEgg at their store and on NewEgg they were still $150. I snatched it up and am still using it.