The charge is hidden. The US dollar, and every other national-bank-backed currency, is debt-based. For every dollar that's put into the economy by the national bank, a bit more than a dollar is owed to the bank. That makes it impossible to pay back the debt without inflating the currency, which reduces the value of the dollar (what it can buy) to less than the original dollar+debt amount.

That's the short version of the explanation I've read about the "evils" of central banks and debt-based currencies. I'm no expert, so I can't really judge the accuracy of this explanation or whether or not it's evil.