A lot of European banks are now introducing negative interest rates on savings accounts, all related to the fact that they're forced to pay the ECB for storing funds.
That's exactly what I meant. I know it on a wealthy level. But for ordinary citizens, it will probably be a monthly increase in the fee. That sells better than a percentage that you might have to raise over time.
Danske Bank (Denmark) recently lowered the threshold for negative interest rates to ~$16,000/€13,300, which is by no means a wealthy level. I wouldn't be surprised if other banks follow their example in the next 24 months.