When you voluntarily tell the world where you are and what you're doing, you make it easy for stalkers to track you. Social network Web sites like Twitter and Facebook invite us to do that through status messages. Most of those sites have made it very convenient for you to post your status from your smartphone, providing streamlined mobile versions of their Web sites plus applications you can install on your smartphone.
Even if you don't say where you are in your status messages, you could be revealing it in your photos. If your smartphone has a camera, it's common practice to take a photo or video and upload it to any of several social networking sites. But whatever is in the background of your photos, like street signs and license plates, could reveal things about who and where you are. Plus, many smartphones geotag your photo when you take it, and that data is uploaded along with your photo, revealing when and where it was taken. If you're trying to avoid stalkers, check the settings on your smartphone to find out how to disable geotagging, and be aware of how different social network sites use and reveal geotags from your photos.
Some social networks are based almost entirely on geolocation. The point is to use your smartphone to "check in" when you're at a particular location, and then have your status updated with your whereabouts. Networks like Mologogo and Google Latitude let you see where people are on a map, while Foursquare and Gowalla turn "checking in" into a fun way to earn rewards. Not only do these sites keep a log of your check-ins, they also let you automatically send status updates to other social networks, like Twitter and Facebook.
In short, if you want to avoid being stalked on your smartphone, treat your smartphone as an extension of your social networks, and take some tips from our article on the Top 10 Things You Should Not Share on Social Networks.