Side note, I am against the Tobin Tax. I think public markets are more important than most folks believe.
I do believe that frequent trading is a good thing, as is retail participation in markets. One of the amplifiers of income inequality, I suspect, in the past few decades has been the fact that high-growth companies that normally would have gone public sooner have stayed private for longer, denying participation from the public market.
For example, a well chosen index of Dot Com stocks that included Amazon, Google, E-Bay etc. picked in 1998 would have, provided there was continuous investment and a long-hold, injected a large amount of capital back into the public and retirement systems, which would have helped lift all boats so to speak.
AMZN was originally at around $4/share (adjusted for splits, provided this data source is correct, https://www.macrotrends.net/stocks/charts/AMZN/amazon/stock-... ), if you had bought 1k stocks of the company in pre-2000, and held until now. Your originally $4k position would be worth 3.2M.
That's quite crazy. And it's retirement money for a lot of people.
Amazon's growth has occurred in the public, giving retail investors the ability to tap into the formation of new wealth. SpaceX's, AirBNB's, DropBox's etc hasn't. They're playthings of the well heeled. Not the gumshoes.
We need to re-orient public markets in such a way that everyone gets to participate in wealth creation. Not restrict it even further.