Holy Katzenjammer Kids! Get a load of this.
You won't even have to be logged in to WoW to buy stuff off the auction house. This is a huge deal. Well, maybe less so for me because I haven't played WoW in years, but it's still a huge deal for the 10 million people who DO, and for the MMO genre in general because you know other companies are going to now feel they have to do this too.
See, a lot of my time back when I DID play WoW was actually spent as a commodities trader, instead of an actual... you know... medieval hero or whatnot. To get the money I needed for expensive things, I actually made most of my fortune in the simple buying and selling of such low-grade crafting components as copper, linen, wool, stone and such. True the prices were low, but it was actually relatively simple to corner the market by buying up everything available for 10 silver and then re-auctioning it for 20 silver. That's literally 100% profit right there, and when you pump hundreds of gold though that machine you get hundreds of gold back.
There's no mention made as to whether you'll be able to SELL things on the auctioneer through this external service, but even the buying part can make it that much more easy to do this sort of thing.
Now if only Warhammer Online would do something similar. Actually, wait... that wouldn't matter because Warhammer Online has no player economy to speak of. Never mind.