Could the "Wikipedia of maps" do to Google what Google's Android has done to Symbian? (The illustration shows the current OpenStreetMaps view of my home town.)
Since it's dependent on user input there's not a lot of there there, but apps based on it are still coming out for the iPhone and Android.
Microsoft is also using OpenStreetMap in Bing. A U.S. unit of the OpenStreetMap Foundation was incorporated earlier this year.
What's possible is illustrated by The Bike Hub, an iPhone app with crowd-sourced data that lets cyclists in England steer around traffic. Reviews are positive, with free satellite navigation (even if a bit kludgy) approved of heartily. (I'd love it if they tracked hills as well as traffic.)
OpenStreetMap says it has 300,000 registered map makers on its site, but that it's the idea behind it -- free data users can adapt to their needs -- that is its most powerful feature.
It's the excitement of user-generated content that Google Maps was trying to access when it opened up its APIs. The question becomes, then, one of how open is open. Google Maps is open like Windows, while OpenStreetMaps appears to be open like Linux.