I think that question is well answered with a variety of the posts here already. Quickly: Q: Is Adsense worth it? A: Yes, if you're willing to put time and effort into it to make it work. If you do your research properly, target the right keywords, build an original, useful site with great content, update regularly, and drive traffic through word-of-mouth, linking, and other strategies, you will find it worthwhile. Q: Why does google ban a user? A: Usually because they violated the TOS in some degree - they clicked their own ads, they provided incentives for others to do so, they artifically inflated clicks or impressions via another means, or else posted ads on a page which goes against the TOS, changed/altered the adsense code, or otherwise were found to be in violation of standards clearly set out by Google.
Than why are most of the people already banned in here.Guidelines forum is full of posts from people who were banned.
Read some more. The banned publishers represent a miniscule number of all Adsense publishers on this forum. You happen to read a lot of posts by banned publishers because they get whiny about being banned and feels the need to run out and tell people about the injustice of it all. As they say, "The squeaky wheel gets the grease." What's the fun (or indeed, purpose?) of posting that you weren't banned?
Like jack said you only see the i'm banned threads. Go to the Reporting/Stats there is were you will see what really goes down with adsense.