Google killed 500 million bad ads in 2014

Google's Bad Ads team banned more than 214,000 advertisers over the course of 2014, disabling more than 500 million bad ads.

It's a sliver of the total traffic on AdWords, but active investigation is a necessary step to maintain the system's reputation, and Google attacks it with the usual pragmatic engineering ethos. Because of the immense scale involved, bad ads are typically flagged through algorithms and then investigated in-person. Google has a number of quirkily named tools designed specifically for that purpose -- the index of ads is known as Beaker, while the analytics tool is called Bunsen -- but the key moment in each case is noticing something's not right. "Once we have a lead on where we think there's going to be problems, we can use those tools to operate on a lot of different kinds of badness," said Ads Engineering director Vikaram Gupta.