Could they just have people sign non-competes perhaps? If you want to work there, it's just part of the package. Seems like a fair trade off to me, and everything is above ground.
Restrictions against non-complete clauses and against forcing employees to assign all intellectual property to employers (even from personal projects) are part of what makes Silicon Valley what it is.
It seems to me that the idea behind this was not fundamentally price-fixing but eliminating the kind of disruption to projects (and inevitable leakage of ideas and technology) you'd get from having people hopping around from company to company. Price fixing may well have figured into it, but I doubt it was the main reason.
"Veridian does love its money." Veronica (Better Off Ted)
Apple and Google could be argued to be "competitors for talent", but if you work on one product at Apple and move to Google and work on something different, there's no state in the country that would consider that a violation of a non-competition agreement. To my knowledge, non-competes are only successfully enforced over trade secrets and client lists.