And in practice, the advertisers make requests that are much more nuanced. They may ask Facebook to show their ad to “liberal Latina women without college education who live in San Antonio and recently got married.” And then they might place a separate ad that is shown only to “conservative African-American women with college educations who live in Austin and are single.” When you click on an ad and are sent to an advertiser’s website, the advertiser knows which ad you saw and thus which bucket you fall in.

Facebook has a lot of data on their users and is eager to monetize it. The advertisers are encouraged to selectively target people according to a mind-boggling range of personal characteristics. Some, such as age, gender or location, are not overly intimate. Others, such as your political views, family size, education, occupation, marital status or interest in a gay dating app, are highly personal.

Facebook would even let advertisers target you based on facts that you may not be aware of, such as that you are a close friend of a soccer fan or of someone who got recently engaged. In a recent study we published, my colleagues and I discovered that advertisers can target users based on their intimate psychological traits, such as personality. If you can think of an important personal characteristic, there’s a good chance it’s targetable on Facebook. Through this ad-targeting system, Facebook discloses facts about you to advertisers, in exchange for money, every time you click on an ad. I’d call that “selling data,” and I bet that you would, too.

But Facebook is extremely clever at dodging this issue. When the company argues that it is not selling data, but rather selling targeted advertising, it’s luring you into a semantic trap, encouraging you to imagine that the only way of selling data is to send advertisers a file filled with user information. Congress may have fallen for this trap set up by Mr. Zuckerberg, but that doesn’t mean you have to. The fact that your data is not disclosed in an Excel spreadsheet but through a click on a targeted ad is irrelevant. Data still changes hands and goes to the advertiser.

Facebook's claiming that it is not selling user data is like a bar’s giving away a free martini with every $12 bag of peanuts and then claiming that it’s not selling drinks. Rich user data is Facebook’s most prized possession, and the company sure isn’t throwing it in for free.