I've noticed this for some time. I thought it was my secret. The totality of the hits on product specific pages overwhelms the hits on index or category pages. Hits on "blue aluminum widgets" are the key and wordtracker and other tools don't show you this. What worries me is that suddenly all of these pages are PR0. Still getting hits though. I was one of the conspiracy theorists that someone mentioned, but now I just think Google is seriously broken and their PHDs can't seem to figure it out.