The two main issues I have with them are that firms tend to give them to just about everybody (instead of just to folks working very directly with real IP), and they only pay base salary, not something closer to actual total compensation (often multiples of the base pay).
Having said that, the quant firm is relatively unimportant and not a good reason to prevent a total noncompete law. It's probably better to just ban them then try and make allowances that aren't full of loopholes.
Cry me a river. If knowledge of some particular employees worth so much to the quant firms, then they should pay them not to leave accordingly.
As a corollary, you may read a patent and now have the knowledge of a product. But you don't have the same legal right to create and sell that product. That right is protected by the patent owner.
If they had not patented whatever it is they had, anyone could replicate the information/item in question with no penalty.
Sure, I suppose someone could develop/copy something in parallel with no knowledge. But that's not really the case in the discussion here as it comes to former employees.
If you worked for Company A which uses a proprietary algorithm for trading and somehow created the same for Company B later, would you really expect a jury to think the two are unrelated? As stated above, the threshold is "more likely than not" that your work for Company B is related to knowing the trade secrets of Company A. If you had never worked for Company A, maybe, but again that's not the case here because a noncompete would never enter the picture.
I mean that’s a tad disingenuous as to how it worked before patents. Patents were meant to dissuade others from copying inventions for a certain set period. It was much rarer to see independent development of the same technology (not that it didn’t happen).