One of the interesting aspects for a blogger might be to know where her/his readers are from. At least, this is something that I would like to know.
Technically, it is not a real problem as every visitor offers its IP address while accessing a website and usually those information and others - like user agent, browser capabilities, preferred languages, etc. - are logged by the web server. Running any kind of log analyzing software like AWStats, WebLog or utilizing external services like Google's Webmaster Tools visualizes that data to the interested site owner.
GeoLocation of 'Get Blogged by JoKi' reader.
Of course, the services of who's.amung.us only displays the locations the very moment you start using their widget. It would have been nice to provide existing web server logs for the initial setup. But, hey... it's a nice gimmick / gadget and it's for free!