Companies that match users online and offline identities generally emphasize that the data is still anonymous because users’ actual names aren’t included in the cookie.

But critics worry about the implications of allowing data brokers to profile every person who is connected to the Internet. In May, the Federal Trade Commission issued a report that found that data brokers collected information on sensitive categories such as whether an individual is pregnant, has a “diabetes interest,” is interested in a “Bible Lifestyle” or is “likely to seek a [credit-card] chargeback.”

Previously, data brokers primarily sold this data to marketers who sent direct mail—aka “junk mail”—to your home. Now, they have found a new market: online marketing that can be targeted as precisely as junk mail.

“Will these classifications mean that some consumers will only be shown advertisements for subprime loans while others will see ads for credit cards?” Federal Trade Commission Chairwoman Edith Ramirez said at a press conference. “Will some be routinely shunted to inferior customer service?”