As in-game transactions and RMT are beginning to become major boons to business the government is getting interested. And, of course, like any good government, they want their share. China was only the first, now Sweden and South Korea are interested in getting their tax laws straight as well.
Taxing game transactions, however, isn't as easy as making laws that tax a physical currency. There's the issues of relative value, constantly diminishing returns as more money flows into virtual economies without enough monetary sinks in the game, and the whole issue if the game goes out of business.
We tend to believe that worlds like this should avoid colliding, but it seems that as we begin to mesh our virtual currencies and begin to value them as much as our real world ones, paths like these seem inevitable.