I turned down an offer from Microsoft, in substantial part, due to their evaluation system and the resulting "competitiveness" of the teams. (The competitiveness was self-admitted during the interview when I asked about the team culture)

I'm not a "star" developer by any means (although I consider myself competent), and I was frankly very concerned that they might be bringing me on to be the "scapegoat" that could be rated underperforming to save the rest of the team.