What does usability and Google Maps have in common. At least one thing, they are synonyms.
Map is the user interface for any data - any. That is the reason why a search engine company acquired a startup that had the keys for that user interface.
We who write map pages, must keep in mind, that we are using map as the user interface because it is the most intuitive way to present any data. Our client or boss may see map as a decoration on the web page. Try to make them see the difference between a list of addresses or that list presented on a map.
I was very delighted to see that a blog called "In usability we trust" talks a lot about Google Maps. The blog is kept by a Swedish guy called Gabriel Svennerberg. He has written some high quality articles about Google Maps API.