A friend has a newish Power Mac and loves the box. Unfortunately it crapped out during an upgrade to Leopard with a hard disk error and had to be reinstalled losing all the data. That was a warning, as just this week the disk died completely to the point of not being seen at boot time or by disk utility. An Apple-care call to Apple was made and a disk exchange was agreed. The standard exchange a faulty part was dispatched under the "DIY repair" process that removes the need for a "return to base" repair but the faulty drive has to be sent back in exchange.
There has been recent concern about returned hardware being "re manufactured" back into the field and service folks rummaging contents so there is reason to worry about data security.
All very good so far but what is that returned disk worth ? The dead mechanicals not very much but the data on the drive can be priceless. It has all his email, password vault and documents. Chances are that the data is not recoverable but that could not be said for some drives returned under warranty. There is now no chance to wipe the disk and mechanical destruction would invalidate the return. He could of course buy his own replacement drive but then that is a waste of the extended warranty payment.
I guess it comes down to a matter for trust or using a drive/account encryption program such as Filevault to prevent data recovery from a lost hard drive.