What are some alternatives?
Storybird - Visual storytelling community
Fanfiction.net - The most popular fan fiction website in the world according to Wikipedia
Storyboard That - Storyboard That is the world's best online storyboard creator.
Little Bird Tales - Little Bird Tales: Capture the Voice of Childhood.
Cowbird - Cowbird is a simple tool for telling stories, and a public library of human experience.
oStorybook - oStorybook : a free Open Source novel writing program for creative writers