Someone can just set up a secret dark exchange on tor if being anonymous is so important.
Well, that's the problem... However anonymous you want to be, there will always be a point along the chain where you want to trade to or from fiat. And unless you meet from person to person to trade some fiat for BTC, or want to trade some higher amount, then there will always be the government keeping an eye on the fiat.
The only way to stay truly anonymous is to not involve fiat at all... And, BTC without a fiat price tag attached to it is worthless (in fiat term...).
Totally agree with this. Right now BTC value is entirely expressed in fiat terms, hence the BTC/USD, BTC/RUR pairs. When Bitcoin is accepted in the mainstream, on the streets as a currency, BTC would no longer need to be associated with fiats but right now... like it or not, BTC needs fiat exchanges.