They just transferred profits from one group of guys that were making fairly easy money, collapsed the profit margin and concentrated that money into a fairly smaller group of people- so I think that they actually did benefit society
Collapse of profit margins is not a necessary ingredient in these, increase in margins is an easy possibility. Except for that, this is an argument for concentration of wealth.
Though I would ask you why all actions have to benefit society? Does a gambler going to a casino benefit society? Does someone who goes to a restauarant? How about about someone who takes a weekend trip away from the city?
I would ask you to read untll the second sentence of my post. Tough, I know.
I am not sure what you are getting at about raising the barriers to entry. Technology has in general raised the barriers to entry for opening up a brokerage firm. It used to be that you needed phones, sales reps, a clearing firm and someone down on the floor to open a brokerage, and that was about it. These days everything is electronic and it is more difficult to do so. That technology needs to be reasonably good as well. To be competitive these days, the technology is commoditized, you can buy many pieces off the shelf.
Confused, self-contradictory. "Off the shelf" and "more difficult" do not go together. Obvious facts that one should know before spouting off on this topic prove this comparison to be idiotic/malicious - Much before moving the trading to the internet, its advantages far outstripped the "costs" of doing so - reach not limited by geography except by law, speed, scalability. AND costs of services and devices needed for internet enablement plummeted. It is not comparable to HFT "technology" because getting one's trade completed microseconds earlierr than without this "technology" is not a "benefit" anyone would notice.