In my neverending quest to plumb the depths of iPhone multisync, I’ve got an update for you fans of ringtones purchased from Apple as well as those you create yourself and sneak into the Ringtones area via Rogue Amoeba’s MakeiPhoneRingtone utility.
As Daring Fireball’s John Gruber points out, the new terms-of-service agreement governing ringtones limits them to a single device:
You shall be able to store Products from up to five different Accounts on certain devices, such as an iPod or iPhone, at a time; provided that each iPhone may sync ring tone Products with only a single Apple-authorized device at a time, and that synching an iPhone with another Apple-authorized device will cause any ring tone Products stored on such iPhone to be erased and, if you so choose, to be replaced with any ring tone Products stored on such other Apple-authorized device.
What this says: If you attach an iPhone containing ringtones to another computer, it will wipe the ringtones. What it seems to mean, however, can be summed up in this screen shot:

In other words, just as music and videos can only be synced together from a single computer, Ringtones are also a part of that party. Note the phrasing in the dialog box: “An iPhone can be synced with only one iTunes library at a time.” Not one computer, but one iTunes library. So syncing your calendar and contacts from one computer, and your photos from another, is fine — but just the single iTunes library (for music, videos, and ringtrones), please.
Note that podcasts fall into this weird gray area, since you can sync them on a different system, but every time you sync with the master iTunes library they get wiped out and must be re-synced.
(Users of Ambrosia’s iToner will be happy to know that iToner completely bypasses this limitation. iToner ringtones are hardy beasts, or stealthy ones.)
"Note that podcasts fall into this weird gray area, since you can sync them on a different system, but every time you sync with the master iTunes library they get wiped out and must be re-synced."
That's interesting to know. Just this morning I was feeling a bit frustrated that some podcasts that I normally sync in the morning before hitting the road weren't available yet, and wondered what the point of not being able to sync FREE podcasts from any machine was.
Sounds a bit kludgy, but if I keep my podcasts and playlists for them the same on both the desktop and laptop, at least I can add missed podcasts during the day while back in the office.
Music is so complex nowadays. It use to be buy it, listen to it. Now it's authorized, one ipod, one computer, whatever. I am glad I don't use the itunes store.