abbeyvet - 9:52 am on Sep 5, 2007 (gmt 0)

Another factor that may affect smart pricing is the time people spend on the landing page, and other factors that are indicative of accidental clicks.

I have no evidence for this, but it makes sense and I believe it may be one way that Google evaluates whether or not clicks are intentional - that the users click because they are genuinely interested in the ad or they clicked because the ad was practically unavoidable, but then backed up or left the landing site immediately.

For example sites which position ads where you would normally expect to find navigation - ie accross the top and down the left - AND remove the navigation from those areas to some unexpected location would be more prone to such accidental clicks and smart pricing and a consequently lower epc.

Blending is a balance - too little and you get ad blindness, too much and people don't even know they are clicking an ad. I don't know how they do it, but I believe that Google are getting much better at detecting and discounting accidental clicks.