I have a large number of sites. Some html, most wordpress. Some on USA servers, some on UK servers. Many use an ad serving solution, a smaller number have CPA Affiliate offers through redirected links, a number also have adsense. I monitor sites against target keywords weekly and noticed some ranking changes 4 weeks ago on the US server sites - the panda roll-out to US Google. Yesterday I saw impacts on the UK server sites from the UK Panda roll-out. Virtually all sites are keyword targeted domain names and most are in the top 100 slots, many on page 1 or 2. Some sites have improved rankings, some have lost positions ( still indexed but - 30 or -40 positions). I have a couple of networks of sites concentrated in two niches. They share heavily spun content and have similar structures. Backlinking has been from some spun articles, light Scrapebox commenting, RSS indexing, some outsourced manual blog commenting (BE and WP). The strange thing at this stage is that they have not all been impacted in the same way. When I analyse the ranking changes there is a very strong correlation with sites that fell and having adsense on the sites. - Typically left hand sidebar and top left hand corner of the article. Now this could be that the adsense sites had the larger visitor volumes (from SERPS) and had more ranking to loose - I am still analysing but thought it might help some folks here to share this. I have now done a series of changes - remove adsense, reduce number of blocks etc in order to see if this makes any change over time. Has anyone else seen anything similar?