Here's a bit of info about the site (sent in a PM):
The web site for Bungie started out around 1996 as Bungie.com. People could go here to find out about Marathon and other bungie games.
Anyway, when we released the game Myth, people had several ways they could play online, TCP/IP, AppleTalk, etc. However, if they wanted to browse for games to play, there was an online service in-game called Bungienet. A companion to that was a web site called bungie.net where people could go to set up their accounts, check out ranks and orders, and get the latest news and updates about playing Myth online.
In light of this, Bungie.net became a far more popular site with quite a bit more traffic than bungie.com ever did. Years later, after the release of Halo 2 and Xbox Live, we finally rolled up all our old web sites (bungie.com, support.bungie.com, seventhcolumn.bungie.net, truth and reconciliation, the myth vault, etc.) into one single site: Bungie.net.
Oh, and yeah, check out the article Antony linked (I'm gonna clean that up).
[Edited on 03.20.2012 2:40 PM PDT]