I think cloud-based computing really excels in 2 areas:
1. Having a backup copy of your data. There are other ways to backup data, so this isn't that compelling for me.
2. Collaboration. If you needed to work with someone on a mastering or mixing project or allow people to 'mark up' your data (soundcloud has this feature, but it's more socializing than collaboration), then I could see where it could be useful.
It seems like cloud photo editing has really taken off. Perhaps because we are primarily visual creatures. Listening to audio seems to be something that people do while they are doing something else (typically visual stuff like web browsing, TV, reading).