It's not really like they had a choice -- they needed to have access to large pools of existing work forces, and agreeing to no-poaching would prevent that.

I'm no fan of Facebook, but in the absence of evidence that they acted tactically, it would seem fair to give them credit for understanding that participating in a cartel is both stupid and unethical.

I would err on the side of caution and look at their previous behaviour as a predictor of future behaviour, which leads me to it being more from the side of necessity than anything ethics wise. You know the story of how Facebook was started yes?

Yeah, it was merely because they were on the sink side of a serious flow. If it was in the other direction they, being a corporation, could easily have been all over an agreement like that.

Was Apple under Jobs the most explicit threat and perhaps that was likely more intimidating for Google than Facebook? I remember reading Jobs threatening some tit-for-tat?