No matter how good your marketing skills are, you’ll make less money on a bad product than you will on a valuable one. Take the time to study the demand for a product before promoting it. Make sure to research the seller with care before teaming up. Your time is worth a lot, and you want to be sure you’re spending it on a product that is profitable and a seller you can believe in.
In the case of cost per mille/click, the publisher is not concerned about whether a visitor is a member of the audience that the advertiser tries to attract and is able to convert, because at this point the publisher has already earned his commission. This leaves the greater, and, in case of cost per mille, the full risk and loss (if the visitor cannot be converted) to the advertiser.