I'm a developer, releasing an iPhone app (Myallo HotList, see http://myallo.com/hotlist ) that uses Twitter geolocation features. I replied in the blog.
I think the main thing Twitter has to do is add some security to the location data. With lots of apps coming that will be able to stick geo data into every tweet, I think it is going to be easy for people to tell an app to add geo location to Twitter, and then forget about it. Being able to restrict who can see that info will be important. I think many people will only want their friends to see location. Maybe a few named friends, maybe just followers, maybe everyone except a few named users, something like that.
