I had an mp3.com site for awhile, but I never really tried to promote it. I got rid of it. I don't like the mp3.com concept, especially the name 'mp3.com' like they own the world. As well, the 'approval' shit and everything else, but that's my bias. Plus, now you have to pay to play to get payed! It's a messed up site IMO.
But, you can't have your music on too many sites. Especially at the rate they dissappear, or become non-functional(lycos).
I guess part of the key would be to get out there and do some real live gigging, pointers to your '.com' site on your biz card or cd handouts, combined with internet promotion. I could see that working with some degree of success. All speculation of course.