Neat concept. I too will vote for text over a map. First off, a "medium sized map of the world" is pretty lousy resolution. Your "dot" would cover an area at least a hundred miles wide, probably more.
Secondly, why bother with the huge bandwidth of a transparent GIF over the first? Why not generate the GIF/JPEG dynamically and place the dots via
a longitude/latitude option we can all set in our user settings?
(I can imagine a dizzying array of tools coming from that. PerlMonks would be calculating the areas of highest Monkly concentration, the bar nearest the most monks, etc)
In general, having your data in text is FAR more flexible than in other formats. You can always generate an image given text data.