Well, I'm not sure how I will be able to contribute yet myself. Although I don't doubt my raw talent, I certainly know the limit of my very limited actual skills
. I still would like to contribute any way which is suitable, if it is just through suggestions, or as a musician.
As regards to a myspace song limit, why not use Soundclick I don't think there is a limit as to the no of uploadable tracks, there might be issues with the bitrate of any uploaded tracks though.
As to the structure of the entire thing I think it is important to have at least some sort of plan as regards how and when the tracks are submitted, just a sort of frame as to prevent the whole thing from falling apart or running on infinitely. I had a few ideas how something like this could be structured, but none of them were really that concrete in my head. It might be an idea to have a look to an/other similar project/s, I'm sure there are plenty.
Also anybody involved should have a relatively clear understanding of what it is this will produce in the end, I mean I'm not sure if the aim of this thing is to make some really awesome music, for the people who take part to learn from it, or if it's simply a way to have a fun time on the internet. There is probably no reason why it shouldn't be all of those if not more though.