Implementation of such a system of control over humanity is very convenient for the world government, because if you leave only one digital currency, you can not only track all transactions, but also prohibit the use of the system to an undesirable person.
Just imagine that we will all someday have a chip containing all the information about us, our movements and all our money. Let's say if my actions are not liked by the government all the funds on my family's chips will be canceled and we just can't buy food in the store. This could indeed become digital slavery and total control over a person's will and thought.
You may be right there but I think it depends on who is in control of the world government leader who understands his flocks would not do such a bad move thing as fully controlling his people. I believe that transparency is a must but we need to preserve human privacy too.
Let's say this chip can only track the record of your super evil deed murder, adultery, etc.. and not invade your other privacy stuff such as what humans normally do in private love and such.