Many new people who have joined Adsense and when they finally $100 the payment threshold frequency of Adsense has got banned and they have declared Adsense as scam or never pay money to its publisher but it is completely wrong. There are many reasons behind a publisher getting banned from Adsense.
Mainly the new publishers do not know the complete or do not read the policies of Adsense and this is a great factor unlike other sites where users does not read the policies. But for Adsense you should know its policies and you should check your site follows or obeys the Adsense policies. May be while applying your site followed its policies and after that the changes you made may be against the Adsense policies.
Then another thing is Adsense calculate earnings at the end of the month and during that time they check the accuracy and fraud click on your website and reduce the earnings while when you reach $100 the payment threshold frequency they check your earnings and check for it accuracy, clicks, invalid clicks for 2-3 times and ensures everything is correct and check whether your sites followed your policies and they ban the accounts and this causes the problem for many users and they declare the Adsense is scam or not paying.
Then another you may say is that you did not click your ads but you must not click there are many another possibilities. Google traces your ip address and stores cookies and check cookies on your computer. If a member from your family or your friends or your neighbours uses your computer and clicks on the ads that are serving under your Adsense id can lead to ban on your Adsense account.
Other things are simple like you should not copy contents from another sites or blog and do not use any copyrighted contents on your site and if you use they should be valid permissions to it for using copyrighted contents. Then you should not place your site on any traffic exchange sites easyhits4u.com, trafficg.com etc such sites because Adsense policies does not allow it. Should not keep more than 3 ads on a page and there are many such things you should know and you should follow it.
So most importantly read the Adsense policies and check your blog or site follows it otherwise when you reach your earnings Google will check your blogs or sites, accounts etc..... everything and if found anything against their policies you will get banned from Adsense and they cancel your earnings. Adsense the best and more paying ad network apart from it they are very strict and if you get banned then you are banned for your lifetime.