Seems like every person I've ever met in M&A has ended up hating life because of their career choice. They seem to burn out in 5 years or so after salting away a million bucks or 3. Was that your feeling doing the HFT thing?
There is 0 social impact. That’s the downside of course - but hey, how many jobs out there are really having any kind of positive social impact ? Not 0, but close to it.
Intraday financial games are zero-sum. What HFTs gain, they leech away from mutual funds and pension funds and retail investors and market makers who operate over a longer horizon.
Regarding social impact, the world does have some demand for liquidity and price discovery. Providing those services is both essential and extremely difficult. It's definitely not the most social good I could be doing with my talents, but I think it's weakly positive.