Two macs and one iPod
I'm in the fortunate position of owning two macs, a PowerBook G4 and a iMac G5. When I bought my G5 i used the migration assistant to sync my two macs. This was great except for a few things:
I couldn't remove the Airport Express signal strength bar
I couldn't remove the battery level indicator
My iPod was constantly being synced with both macs.
The first two were remedied by upgrading the OS to Tiger (I think just running a reinstall would have done it). The last one annoyed me. I didn't realise it was happening until I wiped all of my music from my PowerBook to save hard disk space. The problem was that iPods are linked to specific iTunes libraries. Using the migration wizard had meant that both Macs had the same id for the libraries, so the iPod tried to sync with both. I didn't want to remove iTunes, I still keep a few songs on here, and more often than not, I'll rip CDs to my PowerBook the minute I buy them.
I remedied the situation by closing iTunes, deleting the entire iTunes folder in my Music folder and restarting iTunes. This forced iTunes to rebuild its library and generate a new library id.