Working out is hard. Not the actual lifting and exercising (though that's no picnic either), but just finding the motivation to put your body through something that often runs counter-intuitive to relaxing and being comfortable. Conversely, playing games is a lot of fun. Foursquare found a way to turn telling people you were arriving at a location into a game and it's a huge hit. Fitocracy looks to do the same for working out, and I think it has a shot.
Fitocracy doesn't just implore you to check-in to a gym every day, thankfully, but offers the chance to either "check-in" to specific fitness routines or individual exercises. You'll earn points for every exercise you do, and just like Foursquare there are special achievements to earn for your hard work.
Fitocracy actually takes incentivizing your workout further than Foursquare does for check-ins by offering "quests" that challenge you to complete certain tasks like "Try out three different shoulder exercises within 7 days." You can also participate in workout challenges against other users when they pop-up periodically.
Suddenly, working out isn't something to suffer through, but a game that you can win by doing it harder and longer than the other users of the app. You see the leaders in numerous categories with the tap of your finger, but there's also groups of like-minded fitness individuals you can keep track of and respond to in a Twitter-like messaging system. You can also collect friends like Facebook to see how your pals are doing on their workout regimens.
By borrowing the best bits of numerous social networking apps, Fitocracy has created a highly motivational exercise-based social network that is as comprehensive as it is enjoyable to use. Anyone looking to get more out of their workouts would be wise to check it out.