"If you really want to see a cool “Web 2.0" application, look no further than this sweet visual world / global chat system built by The Midnight Coders . It pretty much freaking rocks."
"...demonstrates bi-directional messaging between heterogeneous (Flash and AJAX) clients and WebORB Message Server. The server performs additional processing to geolocate chat users, injects necessary information in messages so users can plotted on the map."
(Btw, WerbOrb does .NET...Question for the Midnght Coders (love the name): What can we do to get you to play with Virtual Earth and MSN Messenger? MSN has a bunch of APIs and SDKs that you could use).
I'd descibe Map Chat as Flash+AJAX+Google Maps+IP Geolocate+Chat.