http://duckduckgo.com/l/?kh=-1&uddg=http%3A%2F%2Fwww.dmv.org... (every time you click on a search result you actually click on a link like this,which redirects you to the actual page)
Is it just for pagerank?
From memory the main reason they do this is to allow downstream websites to determine if a user was referred to them by DuckDuckGo without the actual search term. IE you know they came from DDG but with no leakage.
I run searchcode.com (which provides a lot of the code doco and sample results) and since this was done I can now determine how much referral traffic actually comes from DDG but have no idea what you were searching for when you click through.
However, I noticed that if you use their HTML version (i.e., use duckduckgo.com/html/<query> instead), that they don't do the click-tracking. The only downside I've noticed is that there's no infinite-scrolling mode, you have to hit "next".
Whether they're still tracking the search queries, though, I have no idea...