So I started using 'foursquare' a couple weeks ago and I'm glad I did! If you haven't heard, it's a "let's turn real life into a game" website and smartphone application. The idea is to use your phone to update your location and compete with your friends on who can visit more places more often. You get points for unlocking different badges as you travel and add tips or suggestions for others.
I'm not really good at the game... even though I'm always on the road and away from home, I constantly forget to update the application. But I've been really interested in the marketing implications of this fun, rapidly-more-popular game. One part of foursquare allows people to add tips and suggestions. For example, one of my Top-12 things to do in Corning, NY is: "Try the mint St. Patty's Day cookie at the Black & White Cookie Cafe." When tourists check their foursquare application (which recognizes their location based on GPS and cell phone towers), it will give them my suggestion.
Imagine visiting a small town or city you've never been before... and there are hundreds or thousands of foursquare users providing insider tips on how to enjoy your visit. It would be like carrying around your own personal guide of "Diners, Drive-Ins, and Dives" provided by the people who know best.
If you're not already playing, check out foursquare.com and give it a shot. If nothing else, it's a lot of fun - and you'll probably beat my point total each week. That reminds me... I have to update my location. Cheers!