I started a thread about that study yesterday - actually I linked to the Chitika page itself [chitika.com], but I withdrew it because I don't think this study is about organic cliks at all - I think it's about Adwords.
For the top three positions, Chitika shows this:
#1 - 34%
#2 - 17% (2x less than #1)
#3 - 11% (3x less than #1)
The AOL data from 2006 showed #2 as 3.5x less than #1 and #3 as 4.9x less than #1. Now that's a major shift. It's not impossible, but it's really big so I begin to question the study.
Then I notice that the first twenty positions Chitika reports add up to 8,253,240 - and that's the same exact number as what they report for the total number of impressions in the study.
1) If the report is based on impressions, then total clicks should be LOWER than total impressions.
2) Some people definitely go beyond page two - and that is not represented at all.
The study may be valid, and just not well explained - for example, what does "a sample of traffic coming into our advertising network from Google" mean and how does the fact that this is restricted to Chitika's "network" skew the sample?