They are providing marketing and retail support for Chrome books, etc. when the hardware manufacturers won't. Interesting. Any benefits will flow to their bottom lines. Downside is if the hardware sucks, the Google stores will have to deal with the flak. We'll see how well this works out.
I think the Google stores can do well if they start small. Customers need support and training for their Nexus and Chromebook devices. Business customers will also have a place to go for service and support on Adsense, Offers, and other revenue generating services. I can imagine Google hosting marketing events to upsell or cross sell advertising to local businesses. Google shoppers can also pick up merchandise at these Google stores to save on shipping or achieve same day delivery. Google has proven that it is an aggressive company willing to follow the competition to steal market share. So when Steve Jobs asked Google what it wanted to be when it grew up, the answer is becoming clear: you.