That is a good question. If someone has a gaming item in WoW which could be sold, or Diablo II, and they never sell it for fiat, but they use it in the context of the game, do they owe any tax?
This is something only a lawyer can answer but I'm not aware of any gamers being charged with tax evasion or told to pay taxes on in game activities. I'm not aware of Second Life activity being taxed until it is cashed out into fiat either. Can someone answer this?