The figure is closer to 43%, and no, it doesn't follow that those ads weren't a waste of money. It only means that someone actually saw them. Google doesn't have clean hands on this, because they take a cut regardless of whether their advertisers are being defrauded, and they pay those who are committing the fraud. In the past I think they've largely looked the other way and cashed the checks. This admission is an indication that they realize they have to go legit, which in the end is going to mean taking a big revenue hit down the road.