No doubt there's more scamming in TA than in QA. As far as quackery, I'm not so sure. As I said, they start with questionable assumptions and that's certainly a form of quackery: assuming that their mathematical models are applicable to the real world when serious scrutiny shows otherwise. They are more concerned with having pretty equations that are solvable than getting real and practical solutions to a less-than-analytical trading reality.
When I worked for second major IB at the time, CMT chartered guys was in first round of layoffs in 2008.
go back to archipelago and come forward, the electronic clearing leaves everyone with a drivers license number so to speak,they were bought up by different houses(morgan,gs,etc) if you can track all the trades for the day and surmise who went long,short ,opening or closing a position,apply a little math to the how many open longs ,shorts at one time,equate it to max speed of an average car or any other like analogy ,you can quant all the intraday moves,estimate max avg long or short ,by moving the market and scaring the bejesus out of that flock of sheep and chase em the other direction ,you see it most days on the close,now take those drivers licences and break down the size traders and do some more figuring
If trend following is ta then there are plenty of examples. John Henry owns the Boston red sox and Liverpool FC is a trend follower.