GeraniumV - 9:44 pm on Mar 4, 2011 (gmt 0)

For years now I've resisted Google's urgings to put more adsense units on my site

If Google Adsense and Search are two seperate depts - you would think that the Adsense dept would want to maximize its earnings. If Adsense ads are causing the problem - it would be logical that the Adsense reps will probably be giving different advice in the future. They want sites running their stuff to rank higher. If they are are truly independant it would be in their best interest to game the search algorithm and pass the info onto webmasters.
As a sidenote has any one else seen a steep increase in epcm since the changes were applied