few weeks ago, Boston Police used Facebook to shut down a DIY punk rock gig by using the rather laughable pseudonym Joe Sly (along with an icon featuring a green mowhawked punk with “Boston Punk Zombie” scrawled above it) to discover the location of the illegal gig. 

This is nothing new, police have been using Facebook as an investigative tool for many years. Police have busted dozens of college kids for underage drinking, authorities used Facebook to find two students who had rushed the field after an Ohio State game, and a student at SUNY College was forced into psychiatric treatment after he posted threatening messages on his Facebook page. All of these stories have raised the issue of online privacy, but the real question is why do people who post their personal details on Facebook assume their postings are private?

If privacy is so important to everyone, why is everyone posting so many details of their lives online?

To be certain, Facebook takes privacy very seriously, and its users take it even more seriously. Facebook users commonly complain about changes to Facebook privacy policies—they often provide links to articles instructing users how to change their privacy settings. Earlier this year Facebook agreed to settle a $20 million class action lawsuit over privacy issues (affected users can expect a windfall of $10 each).

But if privacy is so important to everyone, why is everyone posting so many details of their lives online?

It’s an issue that seems to most directly impacting younger people, who have never known a world without the internet. 

Posting pictures, videos, and tweets recounting every detail of one’s life has become common, but that doesn’t mean people shouldn’t be thinking about the fact that once something is posted to the internet, it can no longer be contained.

Even if you think you can control who sees your online content—based on who you have friended and who you have blocked—you have no control over what those people do with your content. Even messages sent through apps like Snapchat, which allow you to send pictures or messages that disappear after a certain amount of time, are more permanent than people expect. A simple iPhone screen capture can turn what was supposed to be a self-destructing secret message into something that can be preserved, not to mention forwarded, emailed, or posted.

There’s one simple rule for ensuring your privacy online: Don’t post or transmit anything online if you want it to remain private.

Alternatively, you could just avoid doing things that are illegal, immoral, or that would get you in trouble with friends, spouses, or bosses. But who are we kidding here. Just be careful about what you do with the largest tool for mass communication ever in the history of mankind.