Most affiliate programs do not benefit search engine rankings because the link from the affiliate to the merchant doesn’t count as a “vote.” Thus, the merchant will not see a benefit in their Google PageRank and consequently in their search engine rankings. For example, any merchant using LinkShare or Commission Junction will not see such a benefit. That’s because they all use temporary redirects, also known as 302 redirects. That type of redirect, which is the one programmers and site administrators tend to use by default, doesn’t pass the link gain (e.g. Google PageRank) on to the target (final destination) URL. Only a very few affiliate management services allow the merchant to capitalize on the link gain of the affiliate. MyAffiliateProgram.com is one such affiliate solution. So I checked them out, and it turns out that it kinda works. Yes, kinda.
Here’s the problem. The affiliate solution needs to use permanent redirects (a.k.a. 301 redirects) rather than temporary (302) ones. MyAffiliateProgram.com uses what they call “direct links.” Here are a couple examples of affiliate-tracked direct links that they provided me to look at: http://www.myaffiliateprogram.com/?kbid=1001 or http://www.kitchen-universe.com?kbid=1001. But when you visit either of these 2 URLs, there is no redirect at all. Consequently, this creates lots of duplicate pages in Google when Googlebot finds these affiliate-tracked direct links and follows them. Taking the first URL as an example, if you search Google for site::www.myaffiliateprogram.com inurl:kbid you’ll see 6,980 duplicate pages in Google. In other words, these are pages that were already in Google with URLs that don’t have kbid= appended at the end.
Think about it this way: Yes, with MyAffiliateProgram.com a merchant will get PageRank flowing to all the links contained on the countless duplicates of the merchant’s home page that are getting indexed. But because there is no 301 redirect present, MyAffiliateProgram has failed to collapse the link gain to one definitive version of the merchant’s home page. Then search engine spiders come along and index all these versions of the merchant’s home page which compete with the merchant’s true home page (the one without any kbid=). Furthermore, searchers who click on listings in the search results that contain kbid= in the URL will get counted as referrals from the affiliate and the merchant will pay for that. Ouch!
So, buyer beware when shopping for an affiliate management service that passes PageRank to your site. The devil’s in the details.
Any readers want to recommend affiliate solutions that do effectively pass link gain?
UPDATE: Just found this great blog post from Greg Boser that discusses this issue in more detail.