I found one thread asking about it at a WoW forum.http://www.mmorpg.com/discussion2.cfm/p ... 24#3351724
It appears to be a subscription based proxy service. You would connect to their servers then take their path to Wow instead of taking whatever automatic path the internet directs you through. The linked thread also mentions a couple of other similar services.
That's exactly right. The way it works is that WTFast uses a network of proxy servers to short-cut the distance between your computer and the host game server. Currently most publishers have a long daisy chain of servers between you and the game server. Each node and server your game data passes through has the chance of being lost or delayed. If you remove more links of the chain, you improve the speed of exchange of data and increase successful connection.
One description we use is that WTFast is an ISP for gamers.
If you have any questions please feel free to reach out to our support team. Better still, don't just take my word for it, try the service completely for free on WTFast.com.