"Often, Music and Photos & Camera are the two biggest offenders. If you use a service like iTunes Match, you can safely delete the Music cache on your device to free up space. If you sync your device with your Mac to back up photos and videos, you can delete those photos and videos, too."
(That from p. 2 of the article cited above.
Won't that delete them all when you sync another batch? Synching is a holy mystery to me, although I use Dropbox as though I knew what I was doing. ICloud seems to either duplicate or erase the stuff I want to sync, but maybe that's because I'm weak on the difference between synching and garden-variety backing up.
