Backblaze just published their hard drive reliability stats for Q3 of 2015. Again, what sticks out to us is the extreme failure rate of the Seagate ST3000DM001 3TB hard drive. Out of 4,247 drives 30.94% failed just in 2015 and the overall failure rate is 28.46%. We have seen many of these in for recovery.
The full report can be found here: https://www.backblaze.com/blog/hard-drive-reliability-q3-2015/.
Additionally, it can be seen that the Hitachi/HGST drives are currently the best in terms of reliability.
For more info about Backblaze and their offerings for cloud-based backups, click here.