As reported by SlashDot:
"As if having to pay $160 to replace a failed 80-GB drive wasn't bad enough, Dave Winer learned to his dismay that Apple had no intention of giving him back the disk he paid them to replace. Since it contained sensitive data like source code and account info, Dave rightly worries about what happens if the drive falls into the wrong hands. Which raises an important question: In an age of identity theft and other confidentiality concerns, is it time for Apple — and other computer manufacturers — to start following the practice of auto mechanics and give you the option of getting back disks that are replaced?"
I don't think this is Apple that is the problem ... often Seagate/WesternDigital/Hitachi make Apple return the drive to them to get credit for the failed drive - which Apple should get. This being said, I have always wished Apple would give back ANY part they replaced. I always (if I can) do such with my customers when I work on their computers. I do try to keep any kind of power adapter because usually I can fuse different power adapters together to make either a bench/test adapter or a temporary customer exchange unit.