It reminds powerful persons that they can't do their meddling without a chance to be caught. It reminds political advisors to be careful in their choice of words when they write dossiers about other politicians (e.g. the US assessments of foreign politicians). It reminds the military that they can't shoot up every black van that wants to take a wounded person away (e.g. the Apache attack video).
In my opinion it puts a check on exactly that kind of people that can normally do what they want without being held responsible, and I like that.
I think it's a real instrument of direct democracy by showing what "freedom of the press" means, and I find it quite striking in which way many "democracies" fight Wikileaks today. I guess... they have a reason to do so. Wikileaks will find it...