There have been lawbringer articles addressing this before. The primary concern, if I remember it correctly, is that by associating a real Blizzard-supported value for gold to real life money creates a huge legal problem. The first issue is that if you, as a player, go out and make 1000 gold a day and that 1000 gold is worth $5 or whatever, then you've "made" $5 for tax purposes. Yes, this may seem silly, but when you're talking about likely billions of gold being transacted on a daily basis, this starts to become incredibly significant. Also consider that if Blizzard has a "bug" that costs you gold for some reason, right now that gold has no inherent value and thus you have nowhere near a legal right to claim foul.

The long and short of it is that giving gold a real life value creates legal concerns.

The author sounds like he will talk about them next week, but there are a lot of viable methods for reducing the value of gold. The first, and simplest, would be to create another currency (like honor/valor/etc points) that is not able to be traded and is able to be used on purchases from NPCs: such as epic flight, repairs and other costs.

The next option is to allow these points to be "essentially" exchanged through an item exchange. For example, if BoE items were instead set to NEWSTATUS and NEWSTATUS items could be sold to a vendor to generate NEWCURRENCY as well as then allowing players to purchase NEWSTATUS items with their NEWCURRENCY. This is a more complicated example, but essentially it creates a non-transferable system that still allows for some items to be exchanged without the currency being exchanged.

Imagine for a second of the Valor Point vendors included existing in-game BoE's to be purchased for significantly higher costs and if BoE's could be sold to the Valor Point vendor for some large % of that cost. Still allows for BoEs to retain a high value, but eliminates one of the largest gold sinks in the game.