* No install
* Automatic software updates
* No need to back up data yourself
* Easy sharing
* Multi-user editing
* Mix and match with snippets composed by others
* Forking model
* Easy embedding on a webpage
It's really not hard to email someone a Sibelius (etc) file for editing, or even to work together in a session over Skype/Facetime.
I suspect the number of Chromebook owners who can't live without an online music collaboration solution isn't huge.
Finally we're only 1 year old they're more than 10. Give us some time ;)
* No install
* Automatic software updates
* No need to back up data yourself
* Easy sharing
* Multi-user editing
* Mix and match with snippets composed by others
* Forking model
* Easy embedding on a webpage