I don't think bitcoin is that anonymous. I think the freedom og bitcoin is the decentralized peer to peer system. Government will have a hard time centralizing bitcoin because of its nature. About tax, the government can do something about it. So bitcoin transfer or conversion to fiat money can have tax if the government want to impose tax on it.
The government can find a lot of ways to tax Bitcoin if they ever wanted to. If we sought possible ways of doing just that, we might not even come close to what the government could potentially do. But because Bitcoin is not that big of a bird yet, they don't seem to be particularly interested in taxing Bitcoin specifically. Doing that might be prohibitively expansive for the tax agencies, for example, to go after every Bitcoin user for alleged tax evasion only to find out in the end that this particular user is from another corner of the world. The said basically means that if Bitcoin is to become a real pain in the ass, they will try to regulate it on a worldwide scale. So far we can enjoy the lack of true interest from the government.