Building in twitter integration into the iOS might be interesting. Twitter is pretty darn powerful communication device. This is somewhat in line with something I've thought for a while, that social media sites (e.g., facebook, linkedin) are vastly over valued because what they do can eventually be integrated into the OS in a way that makes the social media site irrelevant. Why do I need to upload a picture to facebook from my iPhoto library instead of just designating the photo in my iPhoto library? Sure Facebook can make something easy to use (though their programming isn't really all that good), but how can they compete with the actual OS programmer who builds the first layer of interaction that the user sees when they boot their computer?
Another side note, if Twitter gets integrated into iOS better, then people might spend more time on Twitter and less on Facebook. Look out Facebook, Ping might be about to have its revenge.