====a Wall St transaction/sales tax.====
while generally opposed to new taxes of any kind, i am inclined to think that a tax on bid/ask computer generated "ghosts" that appear for milliseconds/seconds, could make a good trail target. say a charge for bid/asks that don't stay, and are honored, for some length of time, and see how that goes.
that way phony bid/asks that try to move the market prices will cost the computer/non human interaction intrusions would pay, even if a trade is not executed. in my mind that is where the real problem lies, millions and millions of phony bid/ask every second across all markets, all to trying to influence price direction.
Tax them is a start imo, a penalty that they only respect, money out of their pockets, rather than trying to take ours.