Most exclusion clauses are narrow -- limited to work you do in line with your companies current or imminent business interests or done with their equipment. When they are not they are unenforceable in most states, especially Texas which does not look fondly on companies keeping their employees from the market, surprisingly enough.

Not to mention that Carmack was an employee of a company he owned, id, that was later acquired. I doubt he even has an exclusionary provision that he'd signed that was anything but very friendly to how he likes to operate if at all.