The Armory has come a long way now since it was first introduced. Even back then, the idea of WoW having its own database was really cool. The addition of arena calculator a few months ago made it even more than a database but also a place players could visit to manage their arena points needs. The new update to the armory is a login protected feature concerning the guild bank, its contents and logs, together with a better system for filtering searches concerning the guild roster.
Back when I was still in another guild quite a long time ago, our guild master created a link in our guild website that showed the contents of the guild bank character using some web service I'm not entirely familiar with. It was updated as often as possible and basically we had to post in our forums for requests to get something from the bank. The nice thing about that link our guild master made was that, though not always accurate, was viewable while outside the game (well there was no way to view the contents inside the game hehe).
The new armory update to guild banks lends the same kind of convenience to the players as that link my guild master used to have. What a convenience it is to be able to view the guild bank's contents without logging in the game. This is what the armory site is all about. It allows players access to some game information without having to log in. Thanks to the armory site, we don't need to log in to see our talent specs, our gear, our profession stats and now the contents of the guild bank.