In my group of friends there is a bit of an inside joke about starting side projects. All of us are in at least 20 or 30 hypothetical side projects, but really only have one or two active musical endeavors at any given time (with tim as a notable exception).
So I was wondering what the state of online music collaboration websites is. Are there any good ones? Ok... so I realized I should google before I ask... just like you should think before you speak. Kompoz.com is a very cool site.

Basically you just upload a song idea, and then either send it to a friend (or make it available to random users) to add to, and it keeps track of each new version of the song so you can go back.
Then I noticed a developer API. Hot damn! So I got to thinking I could start adding extensions... like adding an inaudible noise pattern to the audio files before the song starts as a homing beacon. Then when the song gets re-uploaded it can sync the two and remove the old track leaving just the stuff that was added. Then it would be like a community multi-track program.
I also noticed the site also doesn't have much support people who want to use it for writing songs among a consistant group of people (say a band *wink*). I could possibly hack together something that makes it more useful to bands for closed collaboration.
Another idea I had that I thought would be cool is if they linked up with the Last.fm api and allowed you to import your music taste into your profile.
Anyway let me know what you think! Talk to me baby... I need your sweet, sexy ASCII text to facilitate communication between us so I can understand what you think about this topic which we are discussing!