My $.02:
I have been occasionally tempted to click on an ad - especially when it was showing me the product I wanted to buy. However when I click those ads, I have to do a lot of work to purchase the product and I dont want to work that hard. It seems that ads are only there to get me to go to the site and spend 10-15minutes figuring out their e-commerce stuff. What a really effective ad would do is market a sale and link directly to the list of products that are being sold. I dont click an ad to go visit a site and explore it. I click an ad because it has shown me what I want to buy. If I have to spend a bunch of time to search out the product on the website that the ad referred to, then I leave and dont bother clicking any more ads.
Hackers of the world, unite!