[hussong]

Not an iTunes user, but I guess some people just want to do a selective sync to certain devices to keep storage use in check and maintain library navigability on the device. That can be quite a bit of work which you wouldn't want to lose to technical failure.

[LeoPanthera]

The "correct" way to do this is to make a playlist of the things you want on your device, and then to tell iTunes to sync to that playlist (or collection of playlists) only.