This reminds me of the woman who actually makes a living running a virtual brothel on the Sims Online. People pay simoleans (or however the online currency is spelled) to her girls (and some boys, I imagine) to have cybersex with them. She takes a cut for running the house. Then she eBays them for actual cash. An example of someone making a living off a virtual commodity, sort of, that the government is not getting a cut of. Taxes are a necessary part of life, and everyone should pay their share.
Still, this seems unworkable in practice. Just the fact that the online games are constantly evolving and new ones sprouting up would create a monumental headache in keeping track of what items are in demand, how much they're worth (if you can even define such a thing, save for a mean price they're selling on eBay for), and all the different places those transactions could be taking place. Also, when do you tax? Can you tax an online trade or gift, where nothing but virtual commodities are exchanged? Or can you only tax when the buyer paid real currency for it? How, then, can you keep track of which transactions were for cash, and which were not?
No, it seems like an idea someone kicked around after an all-nighter on WoW and someone else leaked. And then it got blown out of proportion. :P