My argument would be that GMail didn't need network effects since it was just email and you could easily use GMail while your friends still used whatever they used to use. Contrast to Wave where limited invites kept your friends from using it which kept you from using it.

this music thing isn't a social thing at all really though, it's pure utility and convenience. In this form anyways.

gmail was a product that was superior to anything any one had used before. If they were rolling out gmail today (assuming current gmail exists and is owned by another company) it would not work.