Google showing maps and local listings in the pure organic web search results is nothing new. For example, the image below shows a search for [plumber 10010], NYC plumbers. Now, if you are not in that local listing and you are in the web search results, what are the chances of you getting clicked on? Slim, no?
A WebmasterWorld thread is asking webmasters and SEOs to estimate the degradation of having the local listings mixed into the web search results. The estimates of the loss range anywhere from 10% to 65% depending on who you ask and where the map location is. I'd assume the example above would be closer to 65% but when the maps show up in the middle of the page, maybe closer to 20%?
Tedster of WebmasterWorld said, "I've seen more like 35% to 60% loss." The site references some studies done in the past as well.
Forum discussion at WebmasterWorld.