Lost a hard drive today: a Seagate Momentus 750 GB unit. Well, I still have it, but no access to its content. It was attached to a Seagate GoFlex Thunderbolt?SATA adaptor when both fell off the bedside table midway through a Time Machine backup.
Upon reconnection, it didn't want to spool up, just made whirr-click, whirr-click noises. Ungood noises.
I've replaced it with a Toshiba 1 TB USB 3 HD & that works fine.
As for the content of the buggered drive: no great loss. It's one of two Time Machine backups I keep for the MBA. Since I've had this particular Air for less than 5 months, there hasn't been a great accumulation of backups on the drive.
I was left with an empty 2.5-in HD case. One of the two clones of the MBA I do was just a bare drive I could attach via Seagate GoFlex Thunderbolt, USB or FireWire adaptors. So it's now in the formerly-empty Seagate HD case.