Eioba have published a very good article about the nine most spoken myths around Google Adsense, such as:
1. Wide ads (336×280, 300×250 and 250×250) are effective in many sites, we must included in ours.
2. Is more beneficial to develop sites that use better paid keywords words.
3. High Traffic + High CTR = High Income.
4. Be careful if your traffic suddenly increases, Google may think that you are doing spamming.
5. If Google suddenly bans your Adsense’s account, you will not be able to defend yourself.
6. Google Adsense is going to make you millionaire in a couple of months.
7. Repeating visitors helps to stabilize your earnings.
8. The only way to get money of your Adsense’s account is placing their advertising in every website/blog that we owned.
9. People who got dozens or even hundreds of thousands of dollars thanks to Adsense must own a single site visited by millions every day.
In the complete article you can found the 9 Myth and Facts about Google Adsense, a very good reading for those who want to know more about this novel system.