I don't think anyone is arguing that you shouldn't freely associate. Facebook employees who want to collectively bargain should be allowed to. That's just free association. They just shouldn't be allowed to prevent other employees from not unionizing and working without the union.

And then, lots of people can choose not to unionize. Personally, I think few FBers will unionize.

And then perhaps you could negotiate percentage of gross revenue if you wanted. But they could choose not to give you that. So long as we have free association, that's fine.

Personally, I don't think "percent of gross" makes sense unless you're a founder and "percent of marginal gross" is near impossible to calculate so probably not that. I far prefer the market for labour and employment.

You know how people say "it's not that you can't find engineers; you can't find engineers at what you're willing to pay". Well, if you can find engineers, then all is well.