For webmasters Of Google AdSense, pay attention to your account security, it is very important. But since Google in what website advertising code for webmasters, not a so-called whitelist (whitelist), so anyone can take your account number on a other website. If your opponent has put your code in a violation of the site, and you are not informed of the case, there are many malicious clicks, then it is possible, Google will issue a warning or stopping your account.
If Google allows webmasters, Web site specifies that you can run ads in the background, there's no such problem.