According to Click Forensics, click fraud (illegitimate clicks on per-per-click ads) for 2007 increased 15% over 2006. Key findings from data reported for Q4 2007 include:
- The overall industry average click fraud rate rose to 16.6 percent for Q4 2007. That's up from the 14.2 percent click fraud rate for the same quarter in 2006 and 16.2 percent for Q3 2007.
- The average click fraud rate of PPC advertisements appearing on search engine content networks, including Google AdSense and the Yahoo Publisher Network, was 28.3 percent in Q4 2007. That’s up from the 19.2 percent average click fraud rate for the same quarter in 2006 and 28.1 percent for Q3 2007.
- Q4 2007 click fraud traffic from botnets was 15 percent higher than click fraud traffic from botnets in Q3 2007.
- In Q4 2007, the greatest percentage of click fraud originating from countries outside North America came from India (4.3 percent) Germany (3.9 percent) and South Korea (3.7 percent).
A couple pretty bar charts and click fraud "heat map" of the world can be found here.