Your location data is ONLY shared with others when you proactively decide to “check in” to tell foursquare you’re at a particular place. Each of your foursquare check-ins is saved to your “Check-in History” which allows you to look back at all the places you have checked in since you created your foursquare account. You can delete any or all of your check-ins from the History page on the foursquare website. If for some reason you ever decide to delete your foursquare account, your entire check-in history will be removed from our database.
To view another user’s check-in information, you need to add them as a friend (and they need to accept your invitation), or you need to accept a friend invitation from them. (Our friending model is similar to Facebook’s “friends” rather than Twitter’s “followers”). Only your foursquare friends can see your feed of individual check-ins.
We provide a wide range of privacy controls to all users on the User Settings page. These settings control things such as whether your foursquare friends are allowed to see your email and phone number, whether you want to participate in public Mayorships, whether local merchants can see when you’ve checked into their businesses, and options for sharing your foursquare actions with Twitter and/or Facebook.
Sometimes you’ll want to check in without sharing your specific whereabouts with friends. This is why we created “Private check-ins” — a way of adding places to your check-in history, earning points and adding to your mayor and badge counts, while maintaining completely privacy (even from friends). We find this comes in handy on dates, dinners with parents, or at a coffee shop when you’re just trying to get some work done – really anywhere where you don’t want to friends to drop in. To check-in “privately”, simply select “No” on the “Share this check-in with friends” option seen on every “check-in” screen across our mobile apps.
Twitter and Facebook
Foursquare gives you the option of sharing some of your activity to your Twitter and/or Facebook accounts. Of course, when you publish foursquare check-ins, Mayorships, or badge unlocks to Twitter or Facebook, this information will be viewable by the communities on those services (and in the case of Twitter, may be discoverable by search engines). Please see our FAQs for more information on what happens when you choose to connect your foursquare account to your Twitter or Facebook accounts, and how you can adjust which information you share across these services.
There are currently 20,000,000 FourSquare users. Read more about FourSquare here.