Booyah has released MyTown 4.0 for the iPhone, the latest update to their extremely popular check-in game, and it adds a whole new round of social functions to the system. Properties that you own (which you get by checking-in at real-life properties) can now create items of their own, and different categories, like shopping or dining, will create different types of items. Additionally, items can now be traded with friends in the game, and all of this adds a new level to the gameplay -- not only are you earning points for checking-in, but you're collecting items, and those items can give you extra boosts or otherwise mix up the game.
Plus, actual virtual items helps out Booyah's in-app sales, and I'm sure they will eventually put some of their branding agreements to work by making some of those created items brand-name products. Version 4.0 also adds "location tips," which allow users to leave comments at certain locations (to enable Yelp-style discussions), and check-ins now recharge over time, while max level players can check-in as much as they want.
MyTown's growth has been phenomenal, and with the amount of work going into the app, that growth likely won't slow down any time soon. The app is free and on the App Store right now.