I posted a few things last year about Booyah, an app that promised a lot, but turned out to be not much more than your standard social networking/check-in app. And despite a little hype around its introduction, Booyah had some trouble finding an audience. But the developers (former Blizzard folks still supported by some execs there) came right back with MyTown [iTunes link], and this time, they appear to have hit gold -- despite the app's low profile, it already boasts more users than the well-known Foursquare and Gowalla apps. That's probably because it's more of an actual game; rather than just checking-in, the app has a currency to it, where you can "buy" places you check-in from, and then charge money to the next person that stops by. Imagine Foursquare mixed up with Monopoly -- instead of meaninglessly becoming the mayor of some place you visit, you can actually own and make money off of other people showing up there.
It's an interesting idea, and it seems to be working. MyTown has just reached version 2.0, increasing the number of levels you can earn and items you can buy with the virtual cash. It's still a free app, and originally, we heard that Booyah was going to earn money by teaming up with retail and business partners -- Taco Bell would pay them, and then they'd attach some promotion to checking in from a Taco Bell. But they haven't moved on to that point yet, apparently; right now it's just about building up a userbase and setting up a solid formula. And so far, while the original Booyah app may not have been able to do that, MyTown seems to be rolling right along.