Mozilla put together a nice visualization of firefox 4’s live download stats. Be sure to check out the aggragate breakdown by clicking the donut graph in the bottom left of the screen.
glow.mozilla.org tracks downloads for Firefox 4. When someone clicks the download button on mozilla.com or asks for an upgrade from inside Firefox, we approximate their location based on IP address and store anonymous aggregate location information in our database.
Each dot that shows up on the map represents someone who just downloaded Firefox (with a few seconds of latency as we process everything on the backend). The counter at the top shows the total downloads of Firefox since March 22, 2011, when Firefox 4 was released. The arc chart shows those downloads broken down all the way to the city level.