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.
If it did not provide value to tell the employee the secret then it follows that company would/should not tell the employee the secret.