Megan McArdle is a Bloomberg View columnist. She wrote for the Daily Beast, Newsweek, the Atlantic and the Economist and founded the blog Asymmetrical Information. She is the author of "“The Up Side of Down: Why Failing Well Is the Key to Success.” Read more opinion LISTEN TO ARTICLE 4:13 SHARE THIS ARTICLE Share Tweet Post Email

Photographer: David Paul Morris Photographer: David Paul Morris

You knew that, right? How else would Facebook know to serve that panda video straight into your newsfeed, and leave your college friend’s ill-informed rant about Pacific trade deals in the dark bowels of its servers? How else would it know to serve you with 7,000 ads for wedding dress vendors the very day you announce your engagement? How, my friend, could it deliver that invitation to “like” the Doritos Locos taco when you had only just yourself realized that you were craving terrible Mexican food?

Facebook knows what you like. It knows what you don’t like. It probably knows whether you have been naughty or nice, and will be selling that data to Santa this Christmas season.

This bothers many people, especially since Facebook keeps expanding the list of things it knows about you, and the ways it is willing to use that data to make money. The recent announcement that Facebook would soon target ads using your “likes” and “shares” has triggered some Olympic-level teeth-gnashing from the Electronic Frontier Foundation, because Facebook will get information from you not just when you actually like, “like” something, but when you load a page that has a “like” button on it. They want Facebook to agree to use a “Do Not Track” standard that will keep all that potentially profitable data from the greedy eyes of advertisers.

Of course people should be able to hide data about what sites they use. But there’s a perfectly good way to do this: Stay signed out of Facebook and tell your browser not to accept cookies, or otherwise let advertisers follow you around the web. The problem is, this level of security is incredibly inconvenient, because you have to spend a lot of time painfully re-entering data. The other problem is that naive users, who probably don’t spend a lot of time thinking about privacy, won’t bother.

But what obligation do companies really have to naive users who don’t spend a lot of time thinking about privacy? Some of these users undoubtedly don’t realize that they are exposed, but we should not reject out of hand the possibility that most of them really don’t care enough -- at least, not enough to put up with all that inconvenience. Enforcing someone else’s preferences about privacy may not be liberating; it may be counterproductive.

For let us remember that, dingy and dispiriting as it may be, these companies do need to make money. There’s an old saying in advertising: If you can’t figure out what’s being sold, then you’re the product. “Free” products and services usually aren’t; someone has to finance them, and if they’re not charging you for your use, then they’re charging someone else to use you. Privacy-obsessed folks who carefully hide their activity from the Internet, and ad-hating readers who install blockers, are effectively having their free media and social media platforms subsidized by the folks who don’t know or don’t mind. Because someone has to read the ads that pay the bills.

The interwebs are full of splendid things that social media companies could do to make life easier for various people, and perhaps better for society, if only those social media companies didn’t have to make money. The problem is, if the social media companies implemented them all, they would probably go out of business. That would, of course, take care of problems like Twitter harassment and Facebook’s stalker-like record of your Internet activity, but most people do seem to like having those social media platforms, even at the expense of some exposure to these risks.

No one fix would be unlikely to bring about the death of the firm. But there’s a problem with this, which you see a lot in politics: Someone will say “We’ve got this modest plan, and it would only raise costs (or lower revenue), by some small amount, say, what we could raise with a one-cent surtax on ballpoint pens,” and this is true. Except there are several thousand people who have similarly modest plans, and the next thing you know ballpoint pens cost $20 apiece and the drugstore has to lock them up with the pregnancy tests. The collective weight of the suggestions for improvement (and the third-party software to facilitate same) might well make the Internet kinder and gentler. It might also kill off many of the ways we spend our Internet time.

Privacy matters, but privacy is not free. And the best people to assess the tradeoffs between privacy, access, and convenience are probably the individuals wielding the mouse, rather than the activists wielding the megaphone.

Join a live Q&A with Megan McArdle on BV's Facebook page on Oct. 7 at noon ET to talk about this column. Submit your questions in advance now.

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.