Top Google Ad for YouTube.com goes to scam site
quick.as
quick.as
From what I can gather, Google actually lets their ad customers lie about URL destinations on their ads so that they can use tracking links and such, and apparently isn't really doing anything to validate that the destination URL is ever actually reached.
Google Ads should be considered harmful, at least until they can guarantee the destination of their ads will match the destination Google Search shows users they are going to.
Presumably though, since it's paying itself, Google can afford to outbid anyone on any ad term on their network.
It's actually a little surprising they allow ads on the term at all, actually. For instance, while "Windows support" results are filled with malicious ads at the top, Google has no ads whatsoever for search terms like "Chromebook support". Google actively disables advertising on terms that help their business, and Google does not seem to discourage malware sites on terms that predominantly affect Windows users, for instance.