I have never seen a boom and bust that wasn't perpetuated by government involvement. Bitcoin is immune from such things.
Tomorrow, the UK & USA decide to make investing in Bitcoin illegal, punished by life imprisonment.
Suddenly, Bitcoin crashes and becomes obsolete. Government wins.
USSR banned dollars but it didnt stop them being used anyway. I dont think its that simple, it depends on the bitcoin economy outside the reach of the ban. Bitcoin is banned in some countries usually where dollars are restricted in their circulation
Also you have to weigh the usefulness of bitcoin between people in that banned country territory. If somehow the currency saves them alot of work, stops losses from their flawed national currency then you have alot of demand and people will find a way usually. Bitcoin wallets I think can be passed on usb sticks if need be though it requires more trust, its possible distribution continues anyway even if it were possible to restrict from any live network