Open Radar

 
Summary: (I believe) creating a playlist while you don't have network connectivity can cause thousands of duplicated empty playlists to be created.

Steps to Reproduce:

These are the steps that made it happen for me. I was unwilling to try again because the consequences were so severe that it took 3 iPhones firmware restores to get it back to functional.
1. While you don't have network connectivity (I was in another country with roaming and WiFi turned off, but I believe Airplane Mode also works), create a new playlist on your iPhone. Use as normal.
2. When you come back into network connectivity, there may be thousands of playlists created that have the same name as the one you created offline. They are all empty, having no songs.

Now you are basically stuck with these. I used an Automator workflow to remove all of the playlists from iTunes on my computer, which worked fine. However those changes would not sync onto the iPhone via iTunes Match, it was still stuck with all the empty duplicates which dramatically showed down the Music app. (iPhone 4S).

Even when restoring the iPhone from iCloud, these thousands of duplicate empty playlists were put back on the phone, leaving you with the same problem. The eventual solution was to turn off iTunes Match on the phone, backup to iCloud, then restore from iCloud, which left me with an empty Music app on the iPhone. I was then able to re-enable iTunes Match and use it normally after that.

Expected Results:
- Playlists created offline should sync normally once you come back into network service.

Actual Results:
- Playlists created offline may be duplicated thousands of times, which is extremely severe and almost impossible to get rid of.

Regression:

Notes:

There is a thread on Apple forums where many people have this problem:
https://discussions.apple.com/thread/3505359?start=0&tstart=0