How A/B web testing can unintentionally propagate stereotypes, including racism

Why does Google's ad network think people with names like Latanya and Rasheed have an arrest record?

Imagine the following scenario: An employer is Googling prospective job applicants. Some of those applicants have black-identified names. Due to his or her personal racism, the employer happens to be more likely to click on the InstantCheckmate ads that suggest “Arrested?” next to the black-identified names. And over time, Google’s AdSense algorithm learns that “ads suggestive of an arrest record” work better when associated with black-identified names. Voila.