With last week’s declaration by Twitter that it intends to start identifying places based on the coordinates of geo-coded Tweets, the location land rush is in full swing. A long list of companies including Twitter, Google, Foursquare, Gowalla, SimpleGeo, Loopt, and Citysearch are far along in creating separate databases of places mapped to their geo-coordinates. Mapping businesses, in particular, to the GPS locations near where people are checking in, Tweeting from or pegging a photo is the first step to be able to show them geo-targeted ads, which could help fuel local mobile online advertising in a major way.