yes dani most reason was fraudulent clicl. but there are onther reason like you publish a content which are against adsense policy after they give you mail regarding this if still you not remove then they will ban you.
Mainly the adsence accounts may get baned by the user mistakes. we try to earn more with our webiste and we go with illegial ways. we opt the strategies which avoid teh guideline of Adsence so we get banned.
although google has access to the source of clicks to their ads, the choose instead to use clicks to your domain name to judge if you are exposing their ads to bad traffic. If you have a link cloaker on your domain or a subdomain like the pretty link wordpress plug in to clean up the appearance of your links you can be almost guaranteed that google will ban you even though no bad traffic had a chance to see the adsense ads. try 7search.com for traffic it's cheep and works great.