I don't know what it goes for anymore, but I know WoW had sort of a black market to buy gold.  Their gold was going for something close to 500G per 1USD.  The value of the ingame currency & items are already higher then suggested.  Also, they run the risk of their bank/credit company imposing new fees for jeopardizing their business model.  Small chance, but not one overlooking when your cash cow brings in billions.

The big picture with Blizzard, Microsoft points and Second Life is how games can easily establish their own digital currency.  I am EXTREMELY nervous that Google will partner with Visa or Mastercard and spin off their own commericalized bitcoin.  Many other less secure systems will come about immediately (doesn't facebook have a currency now?), and we'll be left with the same paradigm Linux is in.  People will pay for a Mac with expensive OSX by the thousands versus a cheap PC with a free OS becuase of the commerical appeal.  Why wouldn't they invest and use a commerical coin if Katy Perry told them it is totally cool next super bowl?