Will starting an affiliate program help SEO as dozens, if not hundreds of affiliates around the web start linking to your site? Or will Google and the other engines treat this as paid-links that are unworthy of trust?
The idea for the experiment: make a page, set up an affiliate program, get other SEOs who want results of the experiment to link back.
Hypothesis: If no SEO improvement is noticed, it is reasonable to assume the search engines treated links as paid links. If SEO shows, it suggests Google considers links as vouchers, and trust.
The Heart of the Problem: Does Google trust people's referrals when they have an indirect commercial interest in providing the link? How does Google treat that conflict of interests? Also, does it matter what affiliates are paid for? Is it for sales? For unique clicks? CPM?
Obviously, individual links aren't bought directly from affiliates, so they can't be treated in the same manner.