I've been trying to answer this myself but I can't find it, would any of you know?
Truth is they probably scraped it from someone else initially. See Yelp, Maps (Gmail,Yahoo,Bing,etc), Citysearch, etc. Yahoo has some flexible GeoData APIs. Some of the above also have APIs (including FourSquare) which would make this easier, but is most likely against their terms of service (TOS).
Please post back if you find out otherwise, or a viable solution.
Users generate/add the locations
来源：https://stackoverflow.com/questions/2216198/how-or-where-does-foursquare-gets-its-geodata-from