You have to be really careful with such taxes. Take for instance India: the Indian government places a tax on the exercise of any option. This doesn't stop HFT

You have to be really careful with such taxes. Take for instance India: the Indian government places a tax on the exercise of any option. This doesn't stop HFT at all - it simply makes it more favorable to trade out of a position before exercise. My guess is it mostly hurts the business owner/investor trying to hedge risk. Likewise, a fee on a stock trade would probably have little effect on banks like GS, etc. I imagine it would instead discourage trading through public exchanges and widen spreads - all things that are bad for the little guy.