I actually was far more bullish on Android's prospects before given the rapid device growth, the de facto stealing of Symbian's marketshare and the adoption of the platform as a basic and functional OS for most users. However, as a strategy I think this is quite flawed initially.
As a device maker, Motorola Mobility would be a good play for HTC or Samsung. They'd be integrating an established maker with contracts, devices, patents, etc. For the platform maker to outright buy them would immediately put most other makers on guard.
What guarantee do you have that Google won't favor Motorola? How do you know that they will keep things on an equal footing? You don't. Case in point: travel comparison on AdWords. Google has shown their willingness to integrate vertically and throw valued customers under the bus.
In the long run, it makes absolutely zero sense for Google to keep Motorola as "just another device maker" in the Android ecosystem. They most likely will give it lip service for a year, try and fight off some patent suits and then slowly integrate things much more tightly. I think they're betting that they can become another Apple in terms of integration with Android not being overly harmed by other vendors fleeing to Microsoft. It is the logical strategy - the one driven by reality, not some PR spin of being "open".