I would like all Adsense publishers here to put in their opinions about the possible causes of an Adsense account being disabled with Google stating the reason below (bolded). Please post your thoughts and let us find out the odds why an account can pose a significant risk to their AdWords advertisers and get disabled. I think it's a rather vague reason they tell their AdSense publishers while disabling their accounts. Thanks.
the clicks throughs you are providing have high bounce rate maybe? as an adwords customer I know i don't want that.
The risk that is mentioned is usually simply that advertisers will pay for clicks on their ads that are not 'real', i.e. clicks that were not made by normal people surfing your site, but instead by bots or people associated too closely with the site itself. Those clicks will presumably not lead to extra sales for the advertisers, leading to disappointment on their part, etc. Consider: the giant Google is almost 100% dependent on income they gather from all their Adwords advertisers. If Adwords becomes known as worthless, they have a big problem.
My understanding (from the Adsense Help Forums) is the "risk to our Adwords Advertisers" letter is sent to people who are breaking the Program Policies in some way - so that would include sites with non-allowed content, and sites that don't meet the Google Webmaster quality guidelines. Just like you don't get to pick the ads, the Advertisers don't get to pick which sites their ads appear on, so Google requires sites that show the ads to meet some minimum standards. The "risk" involved would be that many Adwords Advertisers don't want their businesses associated with certain kinds of content (for example sex, alcohol, gambling), which is why there is a "not allowed" list. And obviously most Advertisers don't want their businesses associated with illegal content, like music or video downloads. And sites that are poorly designed, look like spam or otherwise don't have quality content can also reflect badly on the Advertisers. Adwords Advertisers are Google's paying customers, so it only makes sense that the Adsense guidelines are designed to keep them happy.