After months of speculations, Facebook has finally unveiled its geotagging feature. Facebook Places goes live today in the U.S., in partnership with several location-based services. You heard it, it does sound a lot like Twitter's earlier-launched Twitter Places : the name, the partners (at least for Foursquare, Gowalla and Localeze) and the same principle of layering and meshing data from those partners. So what's the difference? Where's the edge?