According to  Twitter's VP of Engineering, the social site has seen more growth over the last nine months than in the previous five years, and that's nothing to the explosion in use that Twitter's expecting to see when Apple weaves it deeply into the software of the iPhone with the upcoming iOS5 update. And this source should know because he's had to tweak Twitter's infrastructure to cope with the flood. The news comes just as Facebook is maneuvering its public image in the press toward a future  as a "mobile" platform, and shortly after efforts to attract users with Facebook phones.
Did Zuckerberg's spine just shiver?
The current speculation  is that Apple's iOS5 and iPhone 5 will arrive in a couple of weeks, and that iOS5 will be suitable for most earlier iDevices. If backwards compatibility is there as expected, the iOS5 install base could include roughly 60 million units already in use (not including some older ones like the 3G iPhone). With the iPad, iPhone 5 (and 4S?), and iPod Touch likely to be popular holiday gifts, and an updated iPad 3 edition due in early 2012, to boot, Apple's iOS device install base could easily top 100 million by March next year.
Wound throughout the core functions of all of these machines sporting Apple's iOS 5 will be Twitter. Not Facebook, or Google+. As far as we can tell from Twitter's assertion  that the integration will let you "Tweet anywhere," hints from Apple itself  and from leaks  showing the functionality from within Apple and Twitter's developer circle, Twitter is included in many of the upgrades and new features iOS5 will bring to the iPhone, and will include just a single effort to set your device up to sign in to Twitter automatically. This means the threshold to access Twitter in order to share a status update, a video clip (from the iPhone 5's allegedly impressive camera) or a relevant web link will be very low--as simple as dabbing at the touchscreen a few times from within whichever app you're using. The camera app is a great example of this, because sharing a new snap on Twitter is as easy as pushing the "tweet" button and adding a caption. But we also know tweeting is just as slickly integrated into Safari, for link sharing, and Maps for sharing your location data.
Using Twitter via iOS is going to be faster than using Facebook, then, because you'll need to seek out Facebook, tap into the app, then enter in your status update...requiring a slightly longer and more deliberate interaction.
While Facebook does have some integration with iOS, and individual third-party apps have also embraced Facebook for sharing information, the fact that Twitter is integrated into Apple's code can't be overstated in importance. Michael Abbot, Twitter's engineer quoted above speaking at GigaOm's Mobilize 2011 summit, expects that developers will rush to embrace Twitter because all the necessary hooks are going to be available directly inside Apple's code--making it easier and perhaps less troublesome to incorporate Twitter's functions.
Of course Facebook will remain hugely popular with both developers and iPhone users. It has its own particular attractions. But people really are lazy, on average. Or at least they want efficient user experiences on mobile devices and online. If Twitter's interactions are easier to use on an iPhone and iPad, then folks may prefer to use Twitter--especially since Twitter's largely avoided the "invasion of privacy" bad press of Facebook. Plus there's the thrill of the "new" if a particular iPhone user hasn't embraced Twitter before.
Meanwhile, also speaking at Mobilize , Facebook's head of Mobile Erick Tseng gained much media attention by saying "within a year or two we'll be a mobile company." Facebook has made no bones that its future is in mobile use, and already about 43% of the active users among its 800 million clients access it while on the move.
But Facebook's got to be feeling the heat from Apple and Twitter potentially ganging up. There's that enormous installed iOS userbase to think about. Then there's iCloud -- Apple's innovative effort to take iTunes into the cloud, and the growing influence of Twitter in the world of music discovery. Today, iTunes is the largest music vendor online, and that's something Apple will try to protect from Facebook's direct attack...meaning we should at least expect users will be easily able to tweet (perhaps automatically) which track they're listenting to from inside the Apple Music app. Facebook's own efforts at music integration are brand new, but already facing criticism (Spotify's "forced" Facebook integration being perhaps the most prominent  example) and the firm's recent big update which included music sharing also landed Facebook in the critic's cross-hairs  because the adjustments again exposed users to unexpected privacy violations. Apple could see this as an opportunity to capitalize on the trusted status it and Twitter have.
There's also social media and mobile advertising to think about. If brands suddenly see a better opportunity to promote their goods and services through Twitter and iPhones, not least because Twitter's user base is primed to suddenly expand, Facebook could take a hit.
Twitter also seems to be planning on leveraging the extra data about its users that'll come from location-awareness in iPhones--Abbot hinted that Twitter will curate some tweets based on location: "I apprecitate information coming to me rather than having to go find it," with an example about news of a local fire emergency. If Twitter is collecting such location data, you can bet it'll also wind this into its advertising plans--which could turn Twitter on iOS into a very powerful location-sensitive advertising platform.
Twitter-Apple may, then, be a very significant threat to Facebook both in terms of cannibalizing some day-to-day use cases from its users, and in offering a mobile advertising platform that could offer even more precise audience targeting. But, let's face it, Facebook's not going to go away and it's already deeply integrated into Apple's biggest competitor smartphone OS Android--which currently outsells the iPhone. Don't expect hundreds of millions of users to flee Facebook for the convenience and assumed "safety" of Twitter on iOS.
But do expect to see changes and threats to Facebook's plans to mobilize itself. A Facebook skeptic may sense a tiny element of fear in its decision to delay launching an official iPad app until the moment of Apple's press event about the iPhone 5  next week--but is this a desperate effort to make sure a corner of the limelight shone around at one of 2011's most highly anticipated tech launches lands on its properties? It could also be a sign that Facebook is trying to make amends with Apple management, after what's reported  to have been a protracted and frustrated (via Facebook foot-dragging) debate over the largely failed Apple social music experiment Ping.