I sync my iPhone both on the work laptop and on the PC at home. At home I have all my music and podcast subscriptions while on the work laptop I have my calendar and a huge address book. Though since 2.0 the iPhone backups all files and this has started to take really long time. Since I only sync the calendar and the address book with the work laptop there is no real need to make a backup there as well. But there is not option in iTunes…

This article explains a very simple method on how to turn it off which worked for me.