I once met a guy who was a programmer for a hedge fund. The strategies and knowledge he had would be very useful to competitors. They didn't have a non-compete agreement in the contract, as this is almost never enforceable here, instead he agreed to a six month notice period - after working two months' notice they then paid four months' salary for him to take a holiday while his knowledge became less and less useful to a competitor. I guess the strategies these guys use only have a limited shelf life but I don't really know much about this sort of work.

Perhaps that sounds like overkill but it feels a bit more reasonable and more fair to the employee - if you want someone to agree to a non-compete then you should agree to pay them for their time where they can't work.