I guess this thread is intended as a reductio ad absurdum, but it really isn't. If you were running a business making virtual goods and selling them in WOW and a lot of your assets were in WOW money, and the value of that money changed, that absolutely should be reflected in your accounts, and it absolutely should affect the amount of tax you owe. Arguably WOW gold should be currency not property, but then the same issue still shows up if you're buying and selling virtual property (say you're a Second Life land baron) which obviously isn't currency, but needs to be accounted for somehow, at least when you start dealing with hundreds of thousands of dollars worth of it.
What seems to be a bit mad in the US is that the tax system seems to have been made deliberately cumbersome, thanks to an unholy alliance of left-wingers who don't like loopholes that they worry rich people will find ways to abuse, right-wingers who like taxes on everyone to be visible and infuriating to encourage people to vote to keep taxes on rich people low, and lobbyists who profit from the current system, for example by selling tax preparation software.
In a lot of developed countries people in normal jobs hardly interact with the tax system at all. In Japan, the employer files most of the paperwork, so you just have a single bit of paper once a year that you give to your employer saying how many children you've got etc, and that's that. To avoid a theoretical (and unenforceable) liability for small capital gains (like the one you make when you buy a cup of coffee with bitcoins) normal countries make the first few thousand dollars tax-free so that if you make a lot of money you have to report it and pay tax on it, but you don't have to waste your and your tax office's time declaring piddling little amounts of money that cost more to collect than they actually raise.
If you're in the US and you'd like to do something about this you could start by following up and voting against the legislators responsible for killing this proposal:
http://www.propublica.org/article/republicans-and-dems-come-together-to-keep-irs-from-competing-turbotaxYou'll have to do a bit of homework to get this right, because the status quo is the result of a long tradition of bi-partisan twattery, and the party labels aren't always a reliable guide.