Google boosted its efforts to boot out rogue and malicious advertisers in the fourth quarter by going after them more aggressively and making it more difficult for them to get back into its AdWords system.
The new, more stringent "cleanup" process began in October, in conjunction with the implementation of new technology that now allows Google to not only blacklist rogue advertiser domains, but also permanently ban them at the AdWords account-creation level.
"We're committed to ensuring that the end user experience is a positive one, and we want users to have a high quality, relevant and safe experience when getting information from our ads," Google spokeswoman Deanna Yick said via email.
"Over the years, we've used a variety of tactics to combat ads that create a poor user experience or direct users to harmful websites. We constantly review and improve our quality systems and are now doing even more to protect users by being more strict with offending advertisers," she added.
Among the banned advertisers are those who charge for supposedly free software, offer get-rich-quick scams or try to lure visitors into disclosing private information in exchange for free products.
"We use both algorithms and manual processes for measuring site quality and identifying scams, and we also listen carefully and take action as applicable when users complain," she said.
Yick would neither confirm nor deny a study released by Internet marketing services provider AdGooroo, which claims that in early December Google kicked out 5.3 percent - more than 30,000 - of AdWords advertisers. She would only say that "scammy" advertisers make up a small minority of the AdWords total.
According to AdGooroo, the ads Google serves per search keyword took a "sudden and precipitous" fall of almost 10 percent last month, from 5.48 ads per keyword to 4.97.
Despite the purge, AdGooroo predicts Google had a financially successful fourth quarter, which is traditionally strong for the company because vendors advertise aggressively during the holiday shopping season.
During the quarter, Google saw an intensification of competition among its AdWords advertisers for placement of their ads, which results in higher prices, according to AdGooroo.
Google also experienced "unusually high" click-through rates, meaning end users clicked on ads more often than usual, AdGooroo said. In its most popular ad format, called pay per click, Google bills advertisers only when someone clicks on their ads.
Moreover, the biggest 80 U.S. retailers spent 12.5 percent more in Google ads in the fourth quarter than the third quarter, according to AdGooroo.