Look at the link to the video of the CBS News interview I posted earlier. The main exchange is already regulated and looks like bitcoin developers will cooperate with regulators.
So the biggest bitcoin exchange is legal. Why is that a bad thing? It actually is a very good thing.
You didn't really think you could avoid paying taxes on dollar profits, did you? If you don't want to pay taxes, don't buy dollars with your bitcoins! Let your bitcoins rest or sell them for goods not for dollars.