If you look at one of the hidden fields in the form that has "partner-pub-xxx" that's his Google account. He's hoping somebody will be dumb enough to put Google Search on their website with his account so he gets credit for the adsense blocks that appear in the search results.
Cool. Maybe I'll stick that search box on one of my adult sites!! Thanks! (No guys, I don't really have any adult sites. I was just making a point.)