New facebook privacy setting allows people to see where you are.
Follow these steps to help protect your privacy:
1) Log in to Facebook. From Account menu, choose Privacy Settings.
Click the Customize option and then click the ‘Customize settings’
link (it’s the one next to the pencil below the table depicting your
current privacy settings).
2) Under the “Things I Share” heading, all the way at the bottom (of
that section), there are two things you may want to change. By default
‘Places I check in’ should be set to only be visible by your friends,
but you may want to limit it to less. Use the drop down menu to do so.
Below that option is ‘Include me in “People Here Now’ after I check
in.” It is enabled by default. This will let people know you’re at a particular location via the location’s page or in a search for people near you. Uncheck ‘Enable” if you don’t want this.
3) Lastly—and this is an important one—go down to the section called
‘Things Others Share’ and find ‘Friends can check me in to Places.’
Initially, they aren’t set to anything at all so the default option could be either choice. Regardless, set this to ‘Disabled’ if you don’t want your friends checking you in. Keep in mind that any friend could potentially check you in anywhere. You don’t actually have to be there. If you don’t want anyone playing a practical joke and checking you in to a strip club, for example, this is a good thing to turn off.
Also, your location can be shared with friends’ applications as well.
To turn that off, you have to go to a completely different section.
Click the ‘Applications and Websites’ link at the bottom and then go
to the ‘Info accessible through your friends’ section. Click ‘Edit
Settings’ and you’ll see a bunch of boxes. Anything checked is
available to Facebook apps that your friends are using. The last
checkbox in this section is ‘Places I’ve visited,’ so uncheck that if
you don’t want your friends’ apps grabbing your location information
as well.
(Thanks to http://lifehacker.com/5616395/how-to-disable-facebook-places
for this info!)