Reply to Yichuan Wang: [I just noticed that Matt Yglesias did a reply that is superior to mine, so I suggest you... http://bit.ly/Pq4ZBM
You can add location information to your Tweets, such as your city or precise location, from the web and via third-party applications. You always have the option to delete your Tweet location history. Learn more
Reply to Yichuan Wang: [I just noticed that Matt Yglesias did a reply that is superior to mine, so I suggest you... http://bit.ly/Pq4ZBM