Earlier quoted context omitted.
Even if you keep your cash in fiat currency cash (i.e. euro notes) you would be safe from this. Keeping your money in some form of cash (whether bank notes or Bitcoin) generally puts you in a worse position than low risk (i.e. diversified) investing. An investment bank which kept accounts in Bitcoin and paid out in Bitcoin would still be at risk of government seizures (unless they operated illegally and hid their ide…
You don't need a bank for your bitcoins. You can keep them in your laptop or smartphone and the Government wouldn't even know you have it there. And even if they did they cannot force you to decrypt your hard drive. You can even keep you bitcoins in your brain. No joke. You can just memorize a passphrase that would recreate an encrypted bitcoin wallet: https://en.bitcoin.it/wiki/Brainwallet
My point was that you can generally earn interest from a bank at better than inflation rates, and if Bitcoin becomes more mainstream, people will do exactly the same thing Bitcoin they do with cash - give control of it over to a bank, and get an account denominated in that currency (i.e. Bitcoin). Once you give the cash or Bitcoin, as applicable, to the bank, you no longer have it in your wallet / Bitcoin address, but instead, the bank promises that it will give you back that amount of Bitcoins, plus interest.
The bank promises to give you back a certain number of Bitcoins, but you don't have any physical way of enforcing that - it is the bank's Bitcoin address that holds them, not yours.
Other people borrow Bitcoins from the bank and have to pay back interest at a higher rate than the bank borrows it. Because of interest, banks collectively are owed more than actually exists in circulation at any one time, so Bitcoin becomes fractional reserve system.
Under this scenario, the government can still tell banks to reduce your balance (which is a number on your servers, and not physically enforced by the Bitcoin protocol). It doesn't affect BitCoins you hold in your own addresses (just like the Cypriot tax doesn't take a cut of money held as cash by individuals in Cyprus), but that might be only a small fraction of the Bitcoin economy in a future under a fractional reserve system.