I think besides getting tax in every transaction which is impossible to be control by the government, Bitcoin will just simply help the economic status of one government. as long as the people benefits then the government will also benefit it will lessen the poor and lessen the corruption.
I was once discussing this topic with one of my friends who is also into Bitcoin. I told him that if bitcoin happens to be legalized, that the government will be charging the users of bitcoin a certain amount of tax, but he never believed it and kept on saying its impossible.
Reasons was because he believed since users are anonymous it will be hard to charge them any tax. Dont underestimate what the government can do, they can easily charge tax on Bitcoin no matter what, they always come up with a plan.