Though a number of mobile Twitter clients have been able to add their own level of geographical information to tweets, Twitter has now officially added geotagging capability to its API (Application Programming Interface).
It doesn’t change how the web interface works, but given that many mobile users (where geotagging is most useful) will use third-party clients, this isn’t much of a problem.
A number of Twitter apps are already using the system (such as Birdfeed, Seesmic Web, Foursquare, Gowalla, Twidroid, Twittelator Pro).
Thankfully, for those wary about privacy issues associated with sharing real-time location information, geotagging is disabled by default, but it’s an easy enough task to turn it on — simply visit the Twitter settings page.
