Really up and down these days. The last few days have been among the worst in years whereas today is back on track (for the moment). Nothing has changed on my sites so I wonder if Google are experimenting with various algorithm factors, especially with invalid click detection. Previous months saw less than 1% taken back at month's end. This last month had closer to 5%. As far as I can see, my traffic is the same - mostly search engines and organic links from decent referrers. Worrying.