No doubt there are examples of people who built a fanbase online from nothing.

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...