Jack and ipwn had it. Though it won't be updating the actual entities and blocks in real time, it still relays your coordinates as you move. The current map updates, I think, when the server restarts. If the map also showed the people moving on the map, the number of users we can have at times can mean that it is tracking (30 on Main+Main2+Creative currently) and reporting those coordinates as they move. As the number of users grows, you can imagine the extra traffic that is going back and forth to update the position. What I do to find my current location is the use F3 or Fn F3 to bring up your coords and then open the world map in your browser. The map shows the current coordinates that your cursor is over on the bottom of the screen. You can also use a minimap such as REI's if you just want to see a "satellite" view of your location.