imho, the API info should have been released to developers before Twitter launched the feature. Isn't that kinda what the company promised to do at Chirp?
TweetDeck has been showing geolocation information for a while so perhaps it was already released? Not sure...
The general geolocation feature has been out for a while, but it's been limited to neighbourhoods like "SoMA, San Francisco", rather than a specific place, like "Twitter HQ, San Francisco."
Seems like this could be a huge leap towards the unified locations database many have called for. Sure it'd be nice if it was an open sourced database, but just like with Facebook and identity, corporate control is currently far more practical.
No mention of the ad platform they're rolling out, a key component of which will be more detailed geo-locating ability to target users, but I would imagine the two are related.