I remember reading a comment very much like this 3-4 years ago about Uber. Can't find it of course, but there was this article 4 years ago https://insights.dice.com/2017/03/08/uber-alumni-trouble-fin... although that is about Uber having a bad work culture, not that working there meant you were ethically compromised which is what I remember being the previous concern - like yours is for FB.