They discuss how sites with quality content can be penalised for employing aggressive (and effective) marketing techniques just because Google doesn’t want to see these sites ranking highly.
This is something I’ve always been very conscious about when looking at affiliate sites and even client sites sometimes. If you want your site to rank for something like “car insurance” you need to make sure that it is better than all the other top 10 results for the same search term. Sure, if you are a huge company you can get away with being just as good as the others but those of you with affiliate sites have to be far better than all the other sites otherwise Google isn’t going to let you rank for long, no matter how many links you have and how old your site is.
Sometimes its better to stay under the radar and not try to rank for the money terms until your site deserves to be there. Nothing will give you a penalty quicker than getting a thin affiliate site to the top of a search term like “mortgages”.