Have you heard of Foursquare yet? If you haven’t, expect to soon. In November, Pete Cashmore, the founder and CEO of the popular social networking news website Mashable, predicted in a column for CNN that Foursquare would be next year’s Twitter. Cashmore isn’t the only one high on Foursquare either. In a blog post last September, tech blogger and web celebrity Robert Scoble did Cashmore one better saying “I think this lame little location game is going to be bigger than Twitter.”

What’s so special about Foursquare? First of all, it is a location-based application. By this, I mean that it is used primarily on GPS-enabled smartphones that can trace a user’s location. The goal of Foursquare is to use the application while you’re out on the town to check-in to different venues. Secondly, as you check-in, you earn points and, eventually, a variety of badges for your profile. If you check-in to a place more than anyone else, you become its “Mayor,” which, in some cases, gets you discounts on products or services.

The competitive aspect of Foursquare (it’s fun to oust someone as the mayor of a place) combined with its function as a sort of mobile city guide make it a fairly addictive application when you’re out. Since I started using the site myself, I have been focused on Foursquare more than almost any other social networking application I use.

As much fun as Foursquare can be to use, however, there are some natural privacy questions about the service. For instance, is it safe to tell the world exactly where you are every time you go out? If someone was monitoring your Foursquare profile, how easily could they establish your pattern of behavior? Before Christmas, we advised our readers not to share their travel details online to help protect their homes from burglary. If you’re using Foursquare all the time, doesn’t the same risk apply?

As Reputation.com CEO Michael Fertik shared in a recent interview with the Financial Times, the dangers of oversharing online are plentiful. Truthfully, effective online reputation management can be a double-edged sword. In order to protect yourself from Internet slander and promote your personal and professional brand, you have to maintain a strong presence online. However, the more you share on the web, the more you have to work at preserving your digital identity.

To this end, the key to using sites like Foursquare (and Twitter or Facebook for that matter) is intelligence and moderation. Consider what you’re sharing before you post it. If you’re late to work because you stayed out late, will you be able to explain it to your boss? Not if they can see that you checked into five bars last night and were out until the wee hours of the morning.

Staying on top of the latest trends in social networking is an important part of proactively protecting your reputation online. Foursquare is a useful and fun tool for finding new places and connecting with friends. As long as you commit to sharing responsibly, you shouldn’t be afraid to try it out.