I can not say I am totally shocked, but I am a bit shocked it happened now. Tons of news on Google Buying a Radio Ad company, Google Agrees to Buy dMarc Extending Its Reach Into Radio (WSJ).
We got AdWords (PPC), we got AdSense (Publisher ads), we got AdPrint (Paper ads) and now we got AdVoice (radio ads). Mike Grehan believes TV is on the way, and I see no reason to argue with that. We also have Danny & Gary at SEW on the topic and Andy Beal where I found the news first.
I'm looking forward to the day when I can control multiple advertising channels through my AdWords interface Exciting stuff!