I wouldn't go so far to say that FB would ever be a resume negative. It really depends on what their experience there was like. Some really great people went to work for FB after making bank a Google in the early days and I would gladly work with any of the folks from that stage of FB. Post that period there was some serious internal culture problems (performance culture SMH) and yeah... I would say most of the good folks (that weren't properly isolated from that misery) left and there was a dark age of FB engineering as a result. I think they recovered from this somewhat but these days it would need to be a case by case basis when I interview a candidate and get an understanding of their time at FB, what they worked on etc and with who.