Social networking gives us a wide reach to broadcast information about ourselves and what we’re doing. But it’s easy to forget just who may be able to access what we’re posting, and how that may reflect on us as individuals. As Facebook’s recent Timeline update demonstrates, what we post to our social networks creates a long historic trail of data about our digital selves.

A story posted this morning on The Next Web reported on a website that highlights just how little thinking goes into so much of what gets posted on social networks. The website, called “We Know What You’re Doing“, aggregates publicly available data from Facebook and Foursquare to call out what can only be viewed as stupid behaviour.

The main page of the site shows a list of status updates from Facebook, divided into four categories: Who wants to get fired?, Who’s hungover?, Who’s taking drugs, and Who’s got a new phone number?. Using Facebook’s Graph API the site is able to pull in actual status updates for each category, complete with a profile photo, first name, and last initial for each user. (I’ve blacked out the names on the screenshot below, but they can be seen in full view on the site).

In another section the site posts actual Foursquare checkins at users’ homes, complete with a photograph of the house or apartment building from Google Streetview. And another section called “Facebook friend checkins” presumably does the same thing as the Foursquare section, but I was unable to access it without granting access to my own Facebook account (which I’m not prepared to do).

At the top of the page, the site proclaims in large type: “We know what you’re doing…”. Then at the bottom of the page it says: “…and we think you should stop.”

The creator of the site calls it an “experiment”, stating “This website is intended to demonstrate the privacy risks that social networking has”.

Indeed.

There are two main takeaways from this experiment:

1) Use privacy controls

You see those “Privacy Settings” on your account? Use them. In Facebook you can even create custom settings within your network, so that different “friends” within your network have different levels of access to what you post. And you can even do it on a post-by-post basis. (I don’t use Foursquare so I’m not sure what privacy options are available there, but if you use Foursquare, look into it.

2) Think before you post

Even if you’ve adjusted your privacy settings, take a second to think about who might see your post, and how it might reflect on your reputation. I’m not saying you should censor yourself or pretend to be someone you’re not – I’m sure I’ve posted things before that have raised a few eyebrows. Just be prepared to explain your judgment if you have to, and to deal with any consequences.

As a general rule: don’t use social media to badmouth your boss, your company, your clients, or for that matter your friends or family members. Save those conversations for the pub or the dinner table (or better yet have a civil, face to face conversation with those concerned).

In short, use common sense.