ClickBank allows you to join for free, and the approval process is virtually automatic, so it’s a great choice for people entering the affiliated game for the first time. ClickBank has a ton of information, including FAQs, walk-throughs, and videos available, so the barrier to entry is quite low. There’s also a (paid) program called ClickBank University with courses and assistance from experienced marketers.
I concluded that having read a product review, people felt more informed to make a purchasing decision. As a result, if they did click a link after reading the review they were more likely to buy the product. Those clicking on the top link seemed to be more in a ‘surfing’ mode. They clicked on the link less because they wanted to buy it but more out of interest to learn more. Some bought the product and some bought other products once they were ‘in the door’ at Amazon.