MarcoPolo is an app for the iPhone and iPod Touch that allows you to geotag your Facebook status. While the concept sounds excellent, the app has a very sketchy feel to it and isn't nearly as useful as it could be.
First off, you need to log into your Facebook account through the app and give it permission. This needs to be done every time unless you select remember me the first time you do it. You give the app full access to all your Facebook info online and offline which isn't really something most people are comfortable with.
Once you finally get it set up after all the back and forth between pages you'll enter what's most likely a blank screen with a status area. You can update your status and it will add the geotag info to your status based on your location when you initially loaded the app. Everyone else you know who uses this app will have their status presented in the same fashion on this page, but how many of your friends are using this app?
Facebook has so many great uses, but unless they offer this feature on their own app, it's not going to take off. Want to geotag your messages and locate your friends? Try Loopt or Twinkle and pass on MarcoPolo, especially considering they plan to charge for it in the near future.