In case you hadn't noticed, AdGooroo today put out some very provocative SEM data which I highly recommend reading; it's available via their blog.
1) They claim # ads per page on Google (U.S.) is down 40% in the last 6 months.
2) "While advertiser counts for all three search engines were flat to lower, it appears that Google and Yahoo have turned up the heat on Microsoft. While Yahoo managed to hang on to its advertiser base (+0.03%) and Google showed a small decline (-6.4%), we observed nearly a 20% drop in MSNís active client count in Q1. Of the three major search engines, only Yahoo has held onto its gains made over the past year. Trailing twelve month advertiser growth for Google, Yahoo, and MSN respectively were -8.5%, +9.8%, and -6.7% respectively."
The question on (1) is, is that big drop real, and if so is it due entirely to G's own efforts to improve ad quality, or is it partly due to macro-economic softening?