* A publicity vehicle for their founders.
* A left-wing political cause (note: I say this as a left-liberal).
* A "fuck-you" to the mainstream media.
* An honest broker of leaked information.
I think when you hang up your sign offering to handle the most sensitive information people have to offer, it's incumbent on you to be above reproach. Clearly, Assange doesn't believe that: he's editorialized their most publicized disclosure to date, throwing their bias and handling of everything they do from this point forward into question.
I don't think it's possible to be above reproach in this day and age. Can you name even one famous person who doesn't have haters, deserved or otherwise?
You say that their goal is to publicize themselves, but to me it seems they're mostly burning bridges with the rest of the world. So, what does publicity buy them? Fame is useless if you can't monetize it, or at least extract something worthwhile out of it.
There's also an issue that I think the author of the (lengthy, but worth it) New Yorker profile nailed:
Soon enough, Assange must confront the paradox of his creation: the thing that he seems to detest most—power without accountability—is encoded in the site’s DNA, and will only become more pronounced as WikiLeaks evolves into a real institution.
If you haven't read it: http://www.newyorker.com/reporting/2010/06/07/100607fa_fact_...