If you are concentrating money in a way you exercise control of, then that money has been realized. If your 'concentration' of money is from loans on stocks, then those stocks value HAS BEEN REALIZED for your benefit, and you should be taxed on your REALIZED gains (you have benefited in the REAL world from the GAINS on your stocks value).

I don't have a problem with concentration of money. I have a problem with playing the game that the concentration of money doesn't actually exist yet and shouldn't be taxed.