A deft move from Facebook after its last privacy furor: the company just told the Wall Street Journal that it's testing a method to track everywhere your mouse moves on the site. Everyone is going to love this!

You know the drill—Facebook wants literally as much information about the human bodies and brains that use the site as possible. You never know what you can monetize until you have it, and of course, the site is already frothing at what it could mean for advertising revenues:

The social network may start collecting data on minute user interactions with its content, such as how long a user's cursor hovers over a certain part of its website, or whether a user's newsfeed is visible at a given moment on the screen of his or her mobile phone, Facebook analytics chief Ken Rudin said Tuesday during an interview.

Mr. Rudin said the captured information could be added to a data analytics warehouse that is available for use throughout the company for an endless range of purposes–from product development to more precise targeting of advertising.

Just think: Facebook could sell ads based not only on the fact that you're a 35-year-old consultant who went to Michigan State and enjoys Battlestar Galactica and The Shins. It can sell ads on all of that, plus the way you move your mouse around—do you tend to hover over, or put your cursor near certain kinds of ads? Boom—that's proof they might be working, even just a little bit, and it'll trigger more of the same.

This means, of course, that Facebook will also know how long you spend hovering over pictures of your ex-boyfriend, or how likely you are to quickly mouse past your friends' cringe-pushing wedding announcements. What it won't know is where exactly your eyeballs are pointed at the page, but with a little coding, the use of your webcam, and the ever-diminishing expectation of what Facebook doesn't know we do in the privacy of our homes, that's not impossible.

Update: A Facebook rep wrote in with the following:

Like most websites, we run numerous tests at any given time to ensure that we're creating the best experience possible for people on Facebook. These experiments look at aggregate trends of how people interact with the site to inform future product decisions. We do not share this information with anyone outside of Facebook and we are not using this information to target ads.

Photo by mioi