Apple took sides while announcing a new operating system for the iPhone, iPad and iPod - iOS5 will have deep rooted integration of Twitter, as opposed to Facebook. Owners of these devices will be able to share tweets, photos, videos and more from all applications by signing-in only once on the device.
The snub to Facebook may not surprise Apple watchers given they had earlier tried a partnership with Facebook for their iTunes' social site, Ping. Could the Ping failure have contributed to them decamping to Twitter? Perhaps.
What does Twitter have to offer Apple that Facebook doesn't? Facebook has close to three times the number of users than Twitter does, but has a very strong user connect agenda which could have clashed with Apple's want of control over its own systems. Twitter, on the other hand, is a more subtle way to connect and could be built as an underlying technology easily.
Also, Facebook has an investment from Microsoft which has deep rooted Facebook integration in its Windows Phone 7 devices. Put these factors together and Apple was bound to be looking for alternatives.
From Twitter's perspective it is a total win-win. They get to be on one of the most famous mobile platforms, across devices. Not only will it add to the number of Twitter users, but give its brand a much needed boost too.