Of course - and everyone already knows that. Youtube was one of the top 10 most heavily-trafficked sites in the world. Google sells adspace. Hmmmm....sounds like a good connection to me!
of course they bought it for the traffic... especially the way they are planning to integrate adsense they are going to make a killing! i personally think that giving the owners of the videos that the ads are on a cut of the adsense profits is a great idea. it will make the ads on the site seem more acceptable too which i guess was their aim
ofcourse they wont buy Youtube just for features but traffice they recieved. I think google will implement something in youtube soon inorder to gain what they have paid for it. ^^