AccuraCast reports that Google tests a new format for local AdWords ads that includes the expandable Maps Plus Box. When you click on the link, Google displays the address of the business, a static map and an option to get directions. This is very similar to what you see next to search results associated with local businesses (e.g.: NY spa).
According to Google, this is a limited test and may not be launched globally. Google has always been reluctant to treat local ads different than the standard ads: even Google Maps used to display ads that sent you to a web page. But things have changed and the ads from Google Maps are placed on the map, the same as the standard results.
Google has also updated the Maps API so that developers can monetize their mashups. "At Developer Day in May, we previewed GAdsManager, a class that would place contextual ad markers for local businesses in a special layer on your map and help you monetize it. We've now released the ads layer with the addition of GAdsManager in Maps API v2.85, and it's ready for early testers."
It's hard to say if integrating an ad into a medium improves the user experience or makes it easier to confuse it with the real content. Google's search results pages contain mostly text, so the targeted text ads are more appropriate than banners, but as Google starts to include more images, videos, expandable boxes in the main results, the ads might become richer and more interactive.