We spend a lot of time thinking about what to post on Facebook. Should you argue that political point your high school friend made? Do your friends really want to see yet another photo of your cat (or baby)? Most of us have, at one time or another, started writing something and then, probably wisely, changed our minds. Unfortunately, the code that powers Facebook still knows what you typed—even if you decide not to publish it. It turns out that the things you explicitly choose not to share aren’t entirely private. Facebook calls these unposted thoughts “self-censorship,” and insights into how it collects these nonposts can be found in a recent paper written by two Facebookers. Sauvik Das, a Ph.D. student at Carnegie Mellon and summer software engineer intern at Facebook, and Adam Kramer, a Facebook data scientist, have put online an article presenting their study of the self-censorship behavior collected from 5 million English-speaking Facebook users.