[jandrese]

> The employer of John Carmack is buying his work product for as long as he remains an employee. The company cannot buy his knowledge and expertise from him, as that is an integral and indivisible part of him.

This is the entire point of non-compete agreements. To deny competitors the expertise the person has developed during their time at your company.

[logfromblammo]

I'm not entirely certain that you read all the way to the end of my reply.

To really lock someone up, you need both a non-disclosure and a non-compete. And anyone worth a non-compete should make it really expensive for the company that is asking for it. You're trading away potentially several years worth of lost opportunity costs to basically not be what you are for some time after leaving a company.