aristotle - 7:17 pm on Nov 23, 2012 (gmt 0)
I have never once seen one shred of evidence that would support the "hypothesis" that noindexing one or even dozens of pages on a site has adversely affected that site's rankings in any way.
I don't see how this proves anything one way or the other. In fact, if the nodexing of some pages has no effect, then it seems to indicate that the Google algorithm continued to take account of the content of those pages even after they were noindexed, which supports my argument.
But let me give a clearcut example. Suppose you have an established site about growing roses. Then you add a noindexed (but crawlable)page full of porn words and you also sell links to porn sites on it, and you also link to it internally. Do you really think that the Google algorithm will totally disregard that page simply because of the noindex tag?