Assange is sympathetic to U.S. Libertarianism, and argues that the free market can flourish only in an ecology of openness and honesty.
"WikiLeaks is designed to make capitalism more free and ethical." Julian Assange.
Here are some essays by Julian Assange explaining his motivations: images/images5/ja-conspiracies.pdf
And here is a longish analysis of those essays: http://zunguzungu.wordpre
This post by Robert P. Baird is a clear and thoughtful articulation of Assange's motives: http://www.3quarksdaily.c