Now is that fun, or what? Trust me! It works just fine! Imagine what more you could exchange with a trick like this! Emails! To-do lists! Pictures! Songs! Movies! Keep on bumpin'! Oh, BTW, you don't need to bump really one phone onto the other! Just shake them both at about the same time and a local connection is established (a... pipe) that feeds contact info in both directions. And the shaking and bumping are pure 'showin'-off' to take some fun advantage of the built-in accelerometer. They could have implemented it with a simple button, but it's more fun this way... feels like magic. The key thing in this app is the ad-hoc establishment of the connection pipe. The rest is just kidstuff!
...There's one more thing! It works fine with iPhones and iPods Touch in all possible pairs (that's 3 to you with ugly scores on school math).