It’s important to note that Wikileaks itself doesn’t choose what information to grab & host; in terms of editorial control, it sits somewhere between pastebin & the New York Times: it mostly receives unsolicited leaks, and it will spend extra effort cleaning up & making accessible things that have wide appeal, but will more or less host anything. Looking at the raw list of leaks makes this clear: there are a lot of items along the lines of the membership list of Condoleeza Rice’s sorority (which is fairly uninteresting).
Does the wikileaks administration reject some submissions? Probably — after all, there are plenty of people who, given a place that will host anything, will use it to pirate hollywood movies & child porn. But, if somebody offers wikileaks an email dump, whether or not they will host it is not even a question: of course they will host it, because that’s what they see as their mission.