From TFA:
I also spent a lot of time on line finding out why people get thrown out of the Adsense scheme and discovered that Google has three sets of rules you can break:
1. The ones in the very long contract that I confess I did not read very carefully
2. The rules that they try to explain in their many pages of Questions and Answers and FAQs
3. The rules they do not tell you about because they are secret and deal with their algorithms