From the Twitter API developer group:

i wanted to give you all a heads up on some big changes we’re making to our  geo-tagging API. (…) people, we find,inherently want to talk about a “place”. a place, for a lot of people, hasa name and is not a latitude and longitude pair. 37.78215, -122.40060,for example, doesn’t mean a lot to a lot of people — but, “San Francisco,CA, USA” does. we’re also trying to help users who aren’t comfortable annotating their tweets with their exact coordinates, but, instead, are really happy to say what city, or even neighborhood, they are in. annotating your place with a name does that too. (…) for this first pass, we’re only going live with United States-centric data,  but that will quickly be expanded geographically as we work out the kinks in our system

What it means: in a move that shouldn’t surprise anyone, Twitter will now enable attachment of “place” information to individual tweets (messages). It’s a brilliant move as people talk about places all the time but they don’t know their latitude/longitude coordinates. By the way, I think lat/long coordinates are for machines, i.e. auto-geolocation tagging. Humans mention “places” when they talk about geography. This means Twitter is starting to embrace structured local data in a way that’s much closer to the DNA of directory publishers. This crystallizes even more the importance of “local” in Twitter’s strategy.