We all know that Google is spending millions for research and development. They came up with Adsense and it became a huge success for them. Their most successful Adsense formats are Large Rectangle (336 x 280) and Medium Rectangle (300 x 250). Have you tried putting Clickbank products exactly as Adsense ads on your web pages? I have increased my income by using this trick. Try this and share your results.
Well... it work for me with any network Those size of banners known to be well converted as long you know to design then right.
Just a small addition to my original post. Try with and without displaying a URL and see whether you are getting different results. You can also try with different types of URLs such as .info and .org
Weather this trick would work or not depends on the niche of your site. If your site target audience are NOT affiliates/web masters when placing ClickBank/CJ/etc products as ads would definitely work.