Via /.: They Might Be Giants now has an online store that they run themselves. This shows how artists (not labels) would likely do things if they were informed and had their way. They sell individual MP3s (that’s right, high-quality MP3, no DRM) and full albums at iTMS-like prices. This seems like a reasonable way to do things. Online music stores might help you find new music, but artists may as well sell songs on their own individual site. Look up the artist on Google, go to their site, buy their music.
Enabling that would seem like a good business. (Of course, you still have to get the labels to agree, or work with unsigned artists.)