There's a regulation that is already functioning for the exchange sites, like in my local exchange,we were required to comply with he KYC Policy and fill up all the information that is necessary. With that rules, we have no choice but to follow and i guess it's just fine because exchange sites are legitimate and they are operating with the license granted by the government.
What I am afraid of to happen, is the time will come that our transaction will be tax..
We cant do anything about that because its been required by the government and exchangers would have no choice but to follow same as you mentioned. Its somehow a good move for exchangers to be registered or legalized because we could assure ourselves on the legitimacy of a certain sites. You said that you were afraid to put or impose taxes on our bitcoin , its an impossible thing to be happen for sure.
Politics and economics have always been so tightly linked to each other. If one day bitcoin and other digital currencies become the main stream and replace centralized currencies, I am guessing there will be changes in government policies as well. After all the nature of bitcoin makes transactions harder to trace, which opens up windows for illegal activities. With this new form of market, the government quite possibly would end up having less and less control.
It would surely changed if these thing would happen on where bitcoin would be the mainstream and the possible effects is on wide ranged as you mentioned government policies would surely changed and more illegal activities would surely rampant because of bitcoins anonymity i think its better to be on this way though thats bitcoin would still remain a digital currency and not the mainstream currency.