The change illustrates the new skepticism with which major marketers are approaching online ad platforms and the automated technology placing their brands on millions of websites. In recent years, advertisers have increasingly shunned buying ads on individual sites in favor of cheaply targeting groups of people across the web based on their browsing habits, a process known as programmatic advertising — enabling, say, a Gerber ad to show up on a local mother’s blog, or a purse in an online shopping cart to follow a person around the internet for weeks.

https://www.nytimes.com/2017/03/29/business/chase-ads-youtube-fake-news-offensive-videos.html