Yeah, don't worry about the threadjacking guys
I should really have clarified a bit better.
I mean how many actually make ONE SALE +
Any affiliate that sends traffic is not useless in the slightest, they are helping you to spread the word about your site, and build brand awareness for you - FREE.
As for the argument about Affiliates and Brand names, the program owners should really SEO their sites properly. I just LOVE IT when I sign up for a program, and see how badly their main sites have been put together - beating them for their own brand phrases in the serps is like taking candy from a baby. They shouldn't gripe about affiliates, they should sort their own shop out first.