What?
So to automatically sync ringtones everything else will be deleted?
I've also had the wonderful problem of iTunes deselecting the "Manually manage music and video" option after I have select it and disconnected my phone. Connecting my iPhone then erases all the music I have added and requires me to resync all my stuff again (a 45 minute process). This has happened 3 times so far.
I sent a nice bug report to Apple.
UPDATE:
I attempted to resync my iPhone to iTunes and checked "Manually manage music and video." Upon selecting "Automatically sync ringtones, I checked the summary tab to verify that the Manually manage music and video was still checked, and it was UNCHECKED! It also does this anytime you select the auto sync option for applications, pictures, etc.
No matter what I do, iTunes insists on removing all my music from my iPhone. Very poor Apple...very poor.