Where I’ve been today, according to the Moves app. Under its new privacy policy, Facebook can access this data, too. (Moves)

Moves is, without a doubt, one of my favorite apps. I probably check it around once an hour, more than anything else but Twitter and e-mail. I’ve found myself changing my habits around it, showing it off to other people, encouraging friends to fork over a couple dollars to download it themselves.

But today I deleted Moves and all its data off my phone. My change of heart springs from the app’s change of ownership: Two weeks ago Facebook bought Moves, which is an “activity diary” that tracks where you go and how you get there. And yesterday, after promising not to mix its data with Facebook’s, Moves quietly amended its privacy policy to let it share all that deeply personal information with its new overlord.

I figure that, through the black magic of cookies, Facebook pretty much knows everything I do online. It doesn’t need to know everything I do offline, too.

But that kind of vast and intimate data is exactly what Moves promises. For ye uninitiated, Moves is kind of like a pedometer or Fitbit: it tracks the steps you walk, the miles you bike, and the distances you bus or drive, displaying that handy data (plus the all-important calorie counts!) in a series of private charts and maps. Do I care if some tech behemoth knows I’ve only walked 1,500 steps today? Not really, no. But I do care if Facebook knows where I walk, and how fast I walk, and what shape my daily routine typically takes.

I have, for instance, developed the expensive, terrible habit of going out for coffee every day around 2 or 3. Moves knows that, which means Facebook does. So Facebook could leverage that information to, say, surface ads about Dunkin Donuts in my feed every afternoon. And that’s just the tip of the proverbial iceberg — in an interview with Buzzfeed last November, Moves’ CEO Sampo Karjalainen waxed poetic on the profound, Big Brother-y potential of movement-based data:

There’s standard location data for sure, but there are also other kinds of contextual data you can collect as well, like which communication method (text, voice, picture) you used and where, scanning calendar entries and the photos you take. You could use the phone’s microphone to listen in on the outside environment while idle and change phone settings and do much more to document different elements of your life. Collecting data from a run or a bike ride is the first step, but then there’s collecting the smaller data that allows you to truly understand your habits and make real changes.

If that doesn’t terrify you, it should. Understanding and changing habits is empowering when it’s you doing the understanding and changing. (That’s why I downloaded Moves to begin with.) But when a massive corporate entity can manipulate my habits for profit, I’m not only not empowered — I’m defenseless against a whole Pandora’s box of corporate (and, potentially, government) surveillance that I don’t really understand.

I have no idea what Facebook is planning to do with Moves’ data, of course. Per Moves’ updated privacy policy, which I read with some distress last night, Moves:

… may share information, including personally identifying information, with our Affiliates (companies that are part of our corporate groups of companies, including but not limited to Facebook) to help provide, understand and improve our services.

That’s vague, and not particularly ominous. (A Facebook spokesperson has since clarified to the Daily Dot that Facebook has no current plans to link user’s Facebook and Moves accounts.) But regardless of how Facebook uses this data, the mere fact that they can theoretically access it is enough to scare me and plenty of other users off.

I’m not naive: I know online privacy is dead. But this seems like a good place to pitch one last, desperate battle against encroachment: I’ve given you my browsing data; leave me alone IRL.