jimbeetle - 4:39 pm on Sep 8, 2012 (gmt 0)

Adsense has an accurate way to detect invalid activity. A site with more than 5,000 page views a day should not get over 3% CTR. Even above 2% is very suspicious. Google knows the average CTR of each market/niche. And if they detect something abnormally high CTR continuously, then they will disable your account for invalid activity. However, for a small site with less than 5,000 page views per day can have a high CTR above 5% once in a while (but not continuously) and that's ok.

You seem very, very sure of these numbers. From whence do they come?