Damn, that Mark Zuckerberg is smart. Facebook could have forked Android and tried to get manufacturers on board, but that would have been an enormous job - and a risky one too, because as Windows Phone's disappointing numbers demonstrate, half-arsed support from OEMs is little better than no support at all.
So rather than compete with Android, Facebook has decided to make it irrelevant instead with Facebook Home.
On a typical Android phone, Facebook is just an app. Android runs the show and gathers all the data, and Facebook exists inside Google's walled garden.
On a phone with Facebook Home, Google's the one in the garden and Facebook's running the show. Facebook knows what apps you're launching, and where you are, and what you're doing, 24/7.
It's an OS in everything but name, then, and because it's an app Facebook can update it and push those updates to users as often as it likes. Nexuses aside, you can't do that with OS updates.
Google must be furious.
Facebook Home isn't for me, or for you: it's not designed for people who worry about privacy, or who take smartphones seriously. It's for the people who don't care too much about tech, the people for whom Facebook and the internet are the same thing.
You can see the appeal of an affordable, attractive Facebook Home phone - and Home is beautifully designed and very attractive - and for people already on Android it isn't hard to imagine the existing Facebook app plugging the hell out of Home until everyone installs it.
What Facebook is doing, then, is trying to cut Google out of Google's own OS - just like Amazon did with the Kindle Fire and perhaps its rumoured Kindle Phone, and just like Chinese manufacturers are doing with their cheap Android handsets.
Google only benefits from Android if we use Google services, give Google data and watch Google ads. That doesn't happen on Kindle Fires, or on Chinese cheapies, and if Zuckerberg gets his way it won't happen on HTCs or Samsungs either. The data will be gathered by Facebook. The ads will be Facebook ads.
That might not happen, of course, but it's a threat - and it's a huge one.
What Facebook is doing, I think, is using Google's strength against it. The very openness that's helped build market share gives Facebook a great opportunity to grab that huge audience, and the lack of control over Android apps means there's no gatekeeper to stop it.
Can you imagine Apple allowing this kind of takeover in iOS?
I'm sure Google will be all smiles about Home today, but I'm equally sure that behind the scenes, Mountain View is Frowny Face Central. Google isn't going to be happy about Home, and that means it'll either try to copy it or kill it.