Well there are also people like Jonathan Coulton (the guy who sings "code monkey") who started with nothing and built a fan base. Also he did the ending song for both Portal games.
But I'm sure it helps a lot if you happen to write songs that appeal to nerds and then get featured on slashdot as a sort of novelty act. I don't see that working as well if you write earnest alt-folk love songs instead of songs about Mountain Dew.
Incidentally, there was a story about Coulton on NPR not long ago [1].
[1] http://www.npr.org/blogs/money/2011/05/14/136279162/an-inter...
Isn't that kind of the whole point though? You can't just be a no-name, release some music that is very similar to a large number of artists in a popular genre of music, and then expect to hit it big.