> Traditional unions (the ones with red flags) would crack down hard on performance based bonus systems.
The reason that unions are against this sort of thing is that instead of being assured a certain salary, what would normally be your salary becomes some performance-based system based on completely artificial statistics, meaning your "base" salary drops overall.
I'm not saying perfomance bonuses are bad , just that 1) it shouldn't replace your salary (especially in high cost-of-living areas like SF , and that 2) It's a lot easier for the company you're working for to game the system than it is for you to attempt to.
The issue is fundamentally the same as other union issues, which is worker protection. Also see things like Silicon Valley companies agreeing not to poach on each others employees (thus lowering salaries for everyone as well).
I'd rather the base salary go up rather than go down, especially in a large company where I'm just a cog in a machine and "performance" is fundamentally a group metric anyways.