I have been keeping a track of clicks on one of my sites and I realised that people who are referred to my site from some related URL OR SEARCH QUERY come and click an ad on my site... the click price multiplies substantially. My normal click is 0.10, Referred click price is Avg $0.75 Thats a fact as I have noticed clicks on the same ad's. I guess PR does play a prominent role afterall. So get your ass moving and get working on some good referral traffic Cheers