Shared online Tracker like Google Docs

I thought of a cool idea for a collaborating tracker.

How hard would it be to make a shared online tracker where every note you add to the tracker I see on my version of the online program as if we were both on the same computer.

Its like google docs for music trackers.

The tracks would have to be able to be encoded and decoded fast and compressed and sent accross the net or peices of the file to tell the other collaborators that are using it right now what changed. Like ajax in an online or off line tracker program.
If you like this idea then comment.