JS_Harris - 3:55 am on Jul 26, 2013 (gmt 0)
I can add credibility to the notion that big brand sites were boosted while the small and medium affiliates of these big brands were hit with traffic losses, I monitored one particular big brand site carefully, but I want to offer an alternative reasoning if I may.
Think about the following very carefully for a second
Big brands gained in traffic while many of their affiliates claimed major traffic losses.
At face value you could theorize that Google boosted big brand sites while reducing rank for their affiliates but it may in fact not be Google's fault at all. What if it is the affiliates themselves who are boosting big brand sites? What if those redirected+nofollowed affiliate links to well known big brand sites have had their nofollow tag and redirect ignored and the links now count as good links?
In short what if Google now says "we trust this big brand site already so your nofollow tags to it are ignored"? It would mean that hundreds of thousands of incoming links would suddenly have boosted big brands while draining affiliate sites. The more affiliate links, the bigger the drain. This would have the effect of cutting out the affiliates and bringing big brands(with affiliate programs) to the top.
It's just a different possibility that comes to the same final conclusion BUT it is one affiliates can control by reducing the number of affiliate links per page and by reducing the number of affiliate pages per site. Balance it out by linking to other authority sites etc.
edit: I cannot find a link to the page at the moment but Matt Cutts asked several months ago if webmasters would mind allowing Google to selectively ignore a nofollow tag. I'd be interested in revisiting the timing of that remark if someone can find it.