Julian Assange has been the subject of a lot of debate recently. He is the one responsible for leaking sensitive US documents through a site known as WikiLeaks. I have not seen the website, so I don't know exactly what material he released. Apparently he released a document recently that showed how NATO had secretly decided to defend Estonia, Latvia, and Lithuania. These documents seem to be aimed at Russia, whose ambassador to NATO demanded that NATO drop the agreement.
This document strains US relations with Russia, and could lead to a massive problem worldwide.
Should the site be allowed to continue, though? I don't really know. This country was in fact founded on free speech, so can they make him keep his mouth shut?
But on the other hand, he is releasing documents that weren't meant to be seen by the world. So the real problem here, in my opinion, is how he's getting these documents. Obviously there's a lack in security somewhere, so perhaps that needs to be fixed first.

Edit: This article was just posted and it seems to be closer to how I look at the situation:
http://tinyurl.com/37a3fy4