Using Google Maps for the Dot exercise?

I know you can use Google Maps to map out a set of data from one source, such as where all of the city parks are located. But that usually starts with a database exclusively controlled by one entity. I also know that you can collaborate on maps with other google users, but you have to give them permission, and they have to be signed up for a google account.

Has anyone seen a case in which multiple (hundreds) anonymous users can add placemarkers (and comments) to a google map?

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The interdisciplinary nature of these challenges justifies a more decisive federal policy that helps metropolitan areas promote energy and location-efficient development.