That is a good post, and after doing a round-up all the microstock affiliate programs at
http://www.microstockinsider.com/referral_schemes I have to say the the crestock one is the best by far!
after switching to crestock from another site (which i'm not going to dis) earnings went up by at least 4 times.
it depends on your situation, they are not always as lucrative as some would let you believe, you have to spend a lot of time 'tweeking', sometimes for little result