See this thread:

Does this sound like ClickBank is allowing merchants to use software that beats the ClickBank affiliates out of their commissions?

It sure does to me, Time to start pulling ClickBank Links, I've got two mall portals and a search engine script too thats now got to go.

This proves that just because you sign up at ClickBank, get your approved linking code from ClickBank and from the ClickBank marketplace you select the merchants you want to promote and then drive target to those merchants site with that links provided by ClickBank, you still may not get paid. Depends on the merchants switch setting that day!!!!

What a crock!