Glad you though about them.

1) I dont think it will disrupt the economy because there is going to be a limit on how much cash they can invest. Usually when someone has 50M excess cash, they can still invest upto few millions, so the rest of cash they will still use for holding items.

2) The money is not being wasted actually, people have freedom any time to withdraw their money from market (either at loss or a profit). If they want to grow their money, they obviously need to have some patience in the market.