@jb: I think you're confusing the fact that an iPod can only sync with one iTunes library and the formatting of hard drive based iPods like the classic and earlier revisions of that same model. Because the iPhone and iPod touch use flash memory instead of actual hard drives with platters, and uses the Apple Mobile Device service, there is no formatting per se on those two products. If you have been syncing your iPod with one computer, and not using the manually manage feature, to modify files on the iPod you must Erase & Sync; this is different from the formatting the OP is referring to.