Update, 1:35 p.m.: Zuckerberg just blew by some important information: This will be available April 12 and only on some as of yet unnamed devices. For now, AT&T and HTC have built the first set of phones just for Home — the HTC First, which comes in four pretty colors. (Ooh la la!) But coming soon, after this "exclusive," Facebook now has a program for other device-makers.
Update, 1:34 p.m.: No mention of how advertising factors into this. Slate's Farhad Manjoo brings up an interesting point — Will there be ads on the "cover feed"? Because that would be terrible.
Update, 1:28 p.m.: So pretty much anyone with an Android phone can get this. If you have an Android, just head to the Play Store. And bam. (Sorry, iPhone and tablet owners.)
Update, 1:26 p.m.: This more in depth "chat heads" demo is convincing. Going in between texts and other apps can be a huge pain on the iPhone and especially Android devices. With this new Facebook version, your conversations with friends pop up right on the screen without having to cancel out the entire app. And it doesn't just work with Facebook messages — it works with SMS, too. Though, it's unclear if they work with something like iMessage?
Update, 1:20 p.m.: Now we're at the demo phase of the presentation, where we get to learn a lot of new vocabulary. "Cover feed," for example, is the name for the home screen that looks like a Facebook Timeline profile, with a big, personalized, full-bleed picture, plus notifications on the screen. Or as Facebook explains it: "Cover feed replaces the lock screen and home screen. It's a window into what's happening with your friends — friends finishing a bike race, your family sharing a meal or an article about your favorite sports team." It looks like this:
Notifications, from Facebook (and other apps) pop up on top of that interface, with their Facebook profile picture. It takes either a swipe or a tap to dismiss or open the messages, a pretty smooth way to say "no thanks," unlike swiping to unlocking an iPhone and either reading or ignoring a text:
Update, 1:15 p.m.: The whole thing is really seamless. For example, the new messaging feature, "chat heads," pops up right in the phone, as you can see below. (That's Sheryl Sandberg, by the way, Leaning In with some texts.) This is one of the best features of the system, making it a lot easier to read and ignore texts without exiting an entire app.
Update, 1:12 p.m.: And here we have it.... Facebook has introduced Home. It look like this when you turn on your phone, which Zuck calls the Cover Feed.
Update, 1:11 p.m.: So, Zuckerberg confirms that Facebook is neither building a phone nor an app because those aren't good enough. Instead we have... Home. The best phones only sell about 10 or 20 million units, which is too tiny for Facebook, Zuck says.