The image to the left is a scatterplot showing the geographic distribution of our subscribers. We update this image every two weeks.
To make this image, we take our database of subscriber addresses and convert them into a lat/lon coordinate using a geocoding service such as this one. Then we take the geocoded dataset and run it through a visualizer/mapper such as this one. All of this, though not as slick as it could be (realtime data visualization would be nice), is all accomplished with free tools.
And no worries. We haven't mapped the complete address and no one else but us has access to your subscription information.