It seems like this problem is well-solved, though not with simple client-list rules. (I've definitely seen those thoroughly violated in ways no one can really enforce.)
Financial firms, for example, give strict noncompetes but back them with actually-valuable payouts. Employees can't be hired away for inside knowledge or clients, because those connections will decay for 6/12/24 months before they start. But their loyalty is actually incentivized, rather than just compelled with "if you quit you're not employable".
Totally agree. Better to use the carrot than the stick, but it never hurts to have the stick as a backup plan.
Typical problem in finance is you have consistent top performers who are compensated very well and would never leave, you don't really need a non-compete for them, deferred bonus is more than enough, but also bring on junior team members who need to learn a lot of confidential information by necessity.
Hopefully all of the juniors become top performers too, but sometimes they don't. It's the middling guys where you worry about them taking all your secrets to another shop. They aren't very valuable to you, so you won't pay them a big bonus, but also not bad enough to fire, and their knowledge is more valuable elsewhere.
Financial firms, for example, give strict noncompetes but back them with actually-valuable payouts. Employees can't be hired away for inside knowledge or clients, because those connections will decay for 6/12/24 months before they start. But their loyalty is actually incentivized, rather than just compelled with "if you quit you're not employable".