Google open sources things when it is beneficial to them to do so, or when it is not very central to their business strategy. Every time an oem takes the android source and makes it run on a new device, they are doing Google a favor, and missing an oppertunity to differentiate themselves from other handset makers.

So yes, it is good to show that there is a way to make money giving away open source software, but i'm not at all convinced it is an example other companies out there right now could actually follow. Google is in a position where they can make lots of money off of people's attention without directly taking their money, so they can afford to give away a MASSIVE piece of software to anyone who asks. Who else could do that? Maybe Microsoft. But I can't think of anyone else. The amount of money and man hours Google has spent on Android must be truly staggering, the fact that they can recoup it on advertising dollars alone is really, really impressive.