There have been a lot of questions lately by affiliates about recommendations on getting ranked to generate more traffic. I was speaking with our SEO Guy about what Google says:

This is an excerpt from an interview with Matt Cutts from Google (Their SEO dude) regarding affiliate links:

Eric Enge: Let's touch on affiliate programs. You are getting other people to send you traffic, and they put a parameter on the URL. You maintain the parameter throughout the whole visit to your site, which is fairly common. Is that something that search engines are pretty good at processing, or is there a real risk of perceived duplicate content there?

Matt Cutts: Duplicate content can happen. If you are operating something like a co-brand, where the only difference in the pages is a logo, then that's the sort of thing that users look at as essentially the same page. Search engines are typically pretty good about trying to merge those sorts of things together, but other scenarios certainly can cause duplicate content issues.

Eric Enge: There is some classic SEO advice out there, which says that what you really should do is let them put their parameter on their URL, but when users click on that link to get to your site, you 301 redirect them to the page without that parameter, and drop the parameter in a cookie.

Matt Cutts: People can do that. The same sort of thing that can also work for landing pages for ads, for example. You might consider making your affiliate landing pages ads in a separate URL directory, which you could then block in robots.txt, for example. Much like ads, affiliate links are typically intended for actual users, not for search engines. That way it’s very traceable, and you don't have to worry about affiliate codes getting leaked or causing duplicate content issues if those pages never get crawled in the first place.

Eric Enge: If Googlebot sees an affiliate link out there, does it treat that link as an endorsement or an ad?

(on affiliate links "... we usually would not count those as an endorsement"

Matt Cutts: Typically, we want to handle those sorts of links appropriately. A lot of the time, that means that the link is essentially driving people for money, so we usually would not count those as an endorsement.

Here is the whole article: