n00b1 - 5:43 pm on Aug 15, 2011 (gmt 0)
Nowhere is Google lucid enough to say "you should use nofollow on affiliate links". The only guidance they offer on this is:
"Links purchased for advertising should be designated as such. This can be done in several ways, such as:
•Adding a rel="nofollow" attribute to the <a> tag..."
Affiliate links are not 'purchased' and Google is not likely ignorant of the big affiliate programs out there. In my case I did say "if you are affiliated with a 'trustable' source there is no reason to try to hide anything from Google". In my case the affiliate links were to a very trustable source that I am no doubt Google is very much aware of as an affiliate provider. And I see no reason to nofollow them (other than paranoia generated from so-called SEOs) if removing this attribute improves the website position in search. Obviously it does depend who you're linking out to and perhaps how frequently - in my case moderation and openness seem to work.