Sgt_Kickaxe - 8:27 am on Oct 19, 2011 (gmt 0)
They have taken aim at affiliates, relevant and useful or not.
Major cosmopolitan cities are preferred targets for spammers, especially hotel affiliates. Such results should be flagged as Spam, even if they are related to the query and helpful to users. For example, a hotel affiliate page with a list of Chicago hotels may be assigned a rating Relevant, but also receive a Spam flag.
The link to the handbook is now hard to find in working order, Google's been busy handing out DMCA requests, but snippets are all over the place like the one I found above. I do NOT have a copy to verify it's accuracy, the snippet above is from a popular SEO blog, but I trust the blog the snippet came from and post it here under fair use rights to discussion.
About the quote above. If you have the BEST website in the world with top notch Google ratings on every page you can still garner a spam rating by displaying a page with affiliate links such as the one mentioned. That appears to affect your entire site, redirect or not. In fact redirects are apparently considered "sneaky" now even if you use them to weed out bots.
Also interesting to note is that much of this has been moved from a manual review to an automated algorithmic approach. You will be told there is no MANUAL penalty if you ask for reconsideration request.