Some time ago, I used Carbon Copy Cloner (CCC) to clone my Cube to my TiBook, so I could have the same OS/software on both machines. This worked great, and I didn't notice any problems at all ... until I bought an iPod. I had the iPod originally "paired" with the Cube, and it worked just peachy. But one day at work I needed to move a 1GB file from one box to another, and I decided to use my iPod as a firewire drive. I hooked the iPod to the TiBook, and as soon as I did, iTunes started, and it auto-sync'd to the iPod, wiping out all the songs on it, since iTunes on the TiBook had no music files.
I talked to my buddy, who has two Macs and and iPod, and he'd never seen that behavior. His iTunes always gave a notice saying that the iPod was already sync'd with a different computer. After poking around, I found out what caused it. In the directory ~/Library -> Preferences -> ByHost, there is supposed to be a file called "com.apple.iTunes.some_string.plist" (where some_string is the machine's Ethernet address in hex). From CCCing the OS, I had two files - one for the Cube's Ethernet address and one for the TiBook. It so happens that the Cube's address is alphanumerically first, and that's what iTunes was picking up.
So when I hooked the iPod to the TiBook, iTunes thought it was connected to the Cube, and since there was no music stored on the TiBook, it wiped the iPod. Deleting the file with the Cube's Ethernet address fixed the issue and made the TiBook's iTunes behave properly.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20030819135554561