One rather extreme example of this is the policy of Reichsfluchtsteuer or Reich Flight Tax implemented in 1931 by Weimer Germany. The law basically was a tax or a seizure of a certain percentage of your assets if you left Germany. At first it was 25%, then it steadily increased to up to 96% by September 1939- the month and year Germany invaded Poland and started World War 2.
Jews were leaving Germany due to persecution. And what better way to fill the Nazi coffers than to seize the assets of Jews.
While this is a rather extreme example of a government sponsored capital control. It just shows you the extent an unrestrained government can do to its people.
Governments today are spending like mad and getting itself into unsustainable level debts. To pay for its spendthrift ways, they must seize from its citizens. Governments cannot produce wealth on its own they have to take it from someone else.
As individual countries get in worse financial shape look for more capital controls and seizure of wealth and income from its citizens or anyone that it can. It could take many forms: default, devaluation, inflation, government intervention in the marketplace, nationalization of certain industries, even more money printing,even more debt, and a host of other tactics. All of which are designed to take from others to pay for promises that they cannot keep.
Fortunately there is a bright side to this madness. Eventually, it fails. Nazi Germany and the Soviet Union were both socialist countries. Both viewed the state as almighty. There was no such thing as individual rights. In both regimes if you hoarded gold and money, kept extra grain or vegetables, or even said or thought anything negative against the state you could be sent to a concentration camp, a Gulag, exciled, or outright shot.
Nazi Germany and Stalin's Soviet Union are examples of government given to much control and abusing their power to where everyone- including it's own citizens were expected to be servants of the state.
Both regimes failed. In the case of Nazo Germany, foreign entities had enough of their tyranical and murderous ways and defeated them. In the case of the Soviet Union, inefficiency and social unrest led to a break up of the Soviet Union.
Today, the United States, Europe, Japan have gotten themselves into too much debt, have created too many promises they cannot fulfill, and are now seizing wealth from its citizens. Eventually their citizens will rise against the tyranny, or their fiat bases Keynesian economc system they have developed will collapse under its own doomed policies.
When that happens, hopefully a more sane market driven, less government intervention, gold (or something valuable) backed based currency system will take its place. Or we could go back to restart and do this madness all over again.