Yes I am sure they are. A lot of what we earn on here may come from Amazon as well as google and hubpages. But there are hubbers who always write around Amazon products so they will earn more than someone who just adds an Amazon capsule to a general hub. For example if you write about baby clothes then obviously the Amazon ads will be relevant, on the other hand if like me you tend to write about health, religion, psychic stuff etc then the amazon ads can be there but may be ignored. Its down to how and what you write.