They can be, but you have to be willing/comfortable going into the OS files and manually deleting them on your PC, then loading those files to your phone.
Doesn't save enough memory to make it worth the hassle, imo
Posted from my CrackBerry at wapforums.crackberry.com
Last time I used crackmem it didnt delete the ringtones. It deleted the wallpaper and preloaded video. But the newer OS version dont have the preloaded video anymore.