When speaking of passing data between applications, I'm specifically thinking of the use cases enabled by Android's intent system. Applications can register the

When speaking of passing data between applications, I'm specifically thinking of the use cases enabled by Android's intent system. Applications can register their ability to respond to and fulfill certain interactions, and then the OS mediates between them. Say, for instance, you're in the Twitter app and click on a link. Instead of embedding a UIWebView, the application fires off a message saying it needs something to display a webpage. The OS then looks at the list of applications that can handle that intent and selects the best one available. If you only have one application that can fulfill that intent, it launches and renders the linked page. If you have multiple browsers, Android prompts you, with an option to remember your preference for that intent. Which means that I can click a link in Twitter and open it in Opera. Or Firefox. Or any third party browser. And then when I open a link in another application, my preferred browser still gets to handle it. The Twitter app doesn't get to own that experience in the same way that it can on iOS, since it's actually backgrounding itself and letting the other application fully handle the task. This also applies to getting directions, calling people, sending text messages, etc. The necessary data (an address, phone number, or message) is transparently shunted from the first app to the next. That dance greatly weakens the boundaries between applications, but enables some really great workflows. Similarly, say I'm looking at my photos and I want to share one with someone. I simply hit the "Share" button, and up pops everything that can handle working with an image. In my case: Bluetooth, Messaging (SMS), Picasa, Twitter, Facebook, Email, and Gmail. Even better, were I to get fed up with the official Twitter client and go install Seesmic, it'd also pop up in that list, automatically, and without any changes to the Photo Gallery itself. Say I install an FTP client. It'll also appear in that list. Google Goggles, too. Any image I can share, I can also send to Goggles for analysis. As far as I know, there's nothing like this on iOS, but I'd be happy to learn that I'm mistaken.