Excellent analysis of Assange's Wikileaks motivations (from the horse's mouth)
tl;dr version (and it is quite long). I've copied out what I think are the key bits, the following is all quoted:He begins by positing that conspiracy and authoritarianism go hand in hand, arguing that since authoritarianism produces resistance to itself -- to the extent that its authoritarianism becomes generally known -- it can only continue to exist and function by preventing its intentions (the authorship of its authority?) from being generally known. It inevitably becomes, he argues, a conspiracy ...the most effective way to attack this kind of organization would be to make "leaks" a fundamental part of the conspiracy’s  information environment. Which is why the point is not that particular leaks are specifically effective. Wikileaks does not leak something like the Collateral Murder video as a way of putting an end to that particular military tactic; that would be to target a specific leg of the hydra even as it grows two more. Instead, the idea is that increasing the porousness of the conspiracy’s information system will impede its functioning, that the conspiracy will turn against itself in self-defense, clamping down on its own information flows in ways that will then impede its own cognitive function. You destroy the conspiracy, in other words, by making it so paranoid of itself that it can no longer conspire ...The leak, in other words, is only the catalyst for the desired counter-overreaction; Wikileaks wants to provoke the conspiracy into turning off its own brain in response to the threat. As it tries to plug its own holes and find the leakers, he reasons, its component elements will de-synchronize from and turn against each other, de-link from the central processing network, and come undone.... he quotes Theodore Roosevelt’s words from his 1912 Progressive party presidential platform as the epigraph to the first essay; Roosevelt realized a hundred years ago that "Behind the ostensible government sits enthroned an invisible government owing no allegiance and acknowledging no responsibility to the people," and it was true, then too, that "To destroy this invisible government, to befoul this unholy alliance between corrupt business and corrupt politics is the first task of statesmanship."