A few days ago I placed some links to Amazon on a few of my sites (these are micro niche sites that are 6-12 months old), and now the rankings that've been stable for months suddenly dropped. The links are incontent ones about related products, and I even tried to cloak them with the Pretty Links plugin. The drops are nothing major, only a few spots, but it means a lot when you're on the upper half of page one. For example one site got from #1 to #4 and another from #3 to #6. Could this drop be related to the Amazon links (because I think I read something similar a few months ago, though I'm not sure), or maybe the plugin? What's the best way to link to related products from your articles in terms of SEO? Thanks!