But for many people, these services remain odd -- and potentially creepy -- tools on your smart phone to let friends or even strangers know you just showed up to a restaurant, gym or the corner deli.
According to a Pew Internet & American Life Project survey this spring, only 5 percent of adult Internet users in the U.S. have used such a service. With the entry of Facebook Places to the mix, though, this number is likely to grow. For now, here is a rundown for the other 95 percent on what Facebook Places means and how to protect your privacy.
1. Checking in.
Most location services won't broadcast your whereabouts without your consent. If you want to tell people where you are, you need a smart phone with GPS or other geolocating capabilities. You begin by installing a free application for one of these services. You then "check in" to a place by choosing it from a list of nearby venues on your screen. You can also add venues on your own. If you don't check in, Facebook won't magically "know" you're there.
2. What's the point?
Many people already tell Facebook friends where they are. Granted, "at the gym" isn't the most insightful status update, but people do it nonetheless. The Places feature builds on this so you can, temporarily, link yourself to a specific place, be it a gym or a burger joint.
If you want, you can let other people who have also checked in -- friends or even strangers -- see that you are there. It's a way to connect your online social network with your offline world. On Foursquare, there's a gaming element, too. Whoever has checked in to a place the most often becomes its virtual "mayor." Users also can earn Scouts-inspired "badges" for checking into specific places -- such as "Gym Rat" for going to the gym 10 times in 30 days. Pointless, scary or genius? You decide.
3. The concerns
The more information you broadcast about yourself online, the more that marketers, strangers, future or current employers and anyone else will know about you. Are you OK with leaving an ever-expanding digital trail behind? Do you want ads to target you based on demographic information you've scattered about? You can walk into a store and then walk out without the owner knowing who you are, but do you know what happens when you also check in, digitally? And should other people be able to share your location with the world?
4. Friends or "friends"?
Under Facebook's default settings, everyone you list as a "friend" will be able to see where you've checked in. But are they really your friends?
Facebook's settings allow you to exclude specific people from seeing your check-ins, or you could authorize only a select few. To do this, go to "Account" on the top right corner of the page. Then choose "Privacy Settings" and click "Customize settings." Look for a pull-down menu next to "Places I check in to." Click on it, and select "Custom."
To authorize people, look for "These people," select "Specific People..." and type their names into the box underneath. To exclude just a few friends -- your boss, maybe, or that nosy co-worker you reluctantly "friended" -- type their names into the "Hide this from" box.
Take this time to go over your full list of friends, with pruning shears if need be. Does Uncle Ned or the spouse of a friend of a friend you met at a wedding last year really need to be there?
5. Checking in friends.
Say you're at a bar with a group of co-workers who are also your Facebook friends. When you check in, you can choose the names of those with you and check them in as well.
That could be useful for Facebook users without smart phones who want to participate, but you may not want your friends checking you in to places, for whatever reason.
Facebook will send you an e-mail notification if a friend tries to check you in someplace.
If you say "Yes," friends will now always be able to check you in. If you choose "Not now," you'll get another notification the next time someone tries to check you in. You can't pick which friends can check you in, nor can you authorize a check-in for one-time only.
To prevent your friends from checking you in once and for all, you have to return to your privacy settings on your computer. Once you're in "Customize settings," choose "Disabled" next to "Friends can check me in to Places."
6. Here now
The "here now" feature lets others -- including strangers -- see that you've checked in to a place. But they can only see this if they have also checked in to the same place in the past few hours.
If this feature is turned off, only your Facebook friends can see your check-ins and your name won't pop up in the "Here now" section of a place.
"Here now" should already be off if your overall privacy settings are at "Friends of Friends" or stricter, something you do through the "Customize settings" section.
If you want to turn it on, click "Enable" next "Include me in 'People Here Now' after I check in" on your privacy customization page. Likewise, if it's already on but you want it off, uncheck the box next to "Enable."
7. Some outside applications could access your check-ins.
To prevent that, go to your privacy settings page. Then click "Edit your settings" under "Applications and Websites" in the lower left corner. Look for an "Edit Settings" box next to "Info accessible through your friends." Click it, and uncheck the box next to "Places I check in to."
8. One more thing on friends
Your friends are hopefully considerate, upstanding, sharp-as-a-tack Facebook citizens. They wouldn't tag embarrassing photos of you without your permission -- so that someone clicking through your profile could pull up images of that wild night with the lampshade on your head and your tie ... well, never mind.
So it follows that they, hopefully, won't check you in to a strip club when you both should be at church, just to be funny. And if they do, maybe it's time to take out those pruning shears.
9. And while you're at it ...
It's a good idea to check your privacy settings on Facebook every so often, so take this time to look at what you are sharing with friends and the broader Internet, and what your friends may be sharing about you. Also look at the photos you've been tagged in over the years and remove any tags that you are not comfortable with. Potential employers often look at applicants' social media pages to get an idea of who they are before hiring.