But if their virtual economy is stabler than a real world economy, this changes, right? I'd rather own ISK than Zimbabwean dollars. Even if it's not strictly stabler, the ISK reflect a certain amount of wealth that's retained in the virtual economy.
Taking another contrived example to make the point obvious, if Eve players basically controlled the equivalent of a trillion dollars, and they all decided to shift half of it to dollars (e.g. Because CCP has decided to print more ISKs), this would have a very real impact on the real economy.
Those are all contrived examples, so regulation shouldn't be based on them, but they show the question is worth considering.