Amanda Hocking is probably the best example right now of an author who made it big through ebooks without having been published traditionally first.

She does have a blog [1] and promotes herself quite heavily through social networks, but she's never had the support of a big publishing house that Konrath had.

She's far from being an overnight success though - in an interview with the Huffington Post [2], she explains how she's been writing fiction constantly from the earliest age, attending every possible writing courses along the way.

1: http://amandahocking.blogspot.com/ 2: http://www.huffingtonpost.com/tonya-plank/meet-mega-bestsell...