Google Map Maker, the crowdsourced mapping Web app launched in 2008 and available in 183 countries, is finally coming to the United States. It's an important addition to Google's mapping services here and could make for maps that are vastly more detailed and useful than they are currently.
In some countries (like Romania, Tech Lead Lalitesh Katragadda told me) Map Maker users have been responsible for creating whole maps from nothing. Here in the U.S., the editing features will allow the addition of more commercial data (stores and other businesses locations) and highly specific street information that's currently missing, like temporary closures due to construction projects. Google Maps, Google Earth, and Google's mobile products will all use this data. Google's route-planning services will take traffic-related updates into consideration.
Katragadda envisions small-town property or business owners taking an interest in how Google represents their location, adding features like nearby park paths to maps to possibly make their neighborhoods look more attractive.
Anyone can edit, sort of Any logged-in Google user can edit a map, but changes from newbies aren't automatically reflected on live maps that the world can see. Users' updates go through a vetting process that asks previously blessed users to approve or deny edits (or send them back for revision). As users get better at getting edits posted without edits, they get closer to unlocking the capability to update public maps without having to go through an approval process, and to becoming moderators themselves to other users' edits.
The idea, Katragadda says, is to make "living and breathing" Google Maps. Fully approved users will see their updates go live "in minutes," and see traffic direction use the updates shortly after that. So owners of mobile businesses, like the new hotness in dining, food trucks, will want to get approved quickly. However, today's announcement does not have a mobile map editor component; the editor requires a full Web browser.