What do Google and Motorola get from being under the same management? Google gets access to Motorola’s home networking gear, GPS devices, cable boxes, and cord/cordless phones, all of which work directly against what Google has been trying to deliver in its Android push. In return, Motorola will destroy third party interest in Android and Chrome OS, while doing nothing to provide Google with the retail stores, PC platform, and local software experience it lacks.
I don't think the platform is doomed. I think Google just lit the fire for HTC and Samsung to develop competing operating systems that really can compete with Android and iOS. So far, they've gone with Android because it's "free" and "open". Now, there is new reason to innovate. It's arguably a more competitive landscape today than it was this time last week, and while the acquisition may hurt Google in the short-to-medium term though integration confusion, this is likely a win for innovation in the market.