CDO: The guy getting all the worst performance reviews, because when he successfully turns the company away from a bad decision there's no real proof of it. Yeah, maybe he just saved $20 million from being dumped in a rathole, but we'll never know.
As someone who was a non-appointed CDO at a company (only because no one else had the backbone to say no) my performance reviews were fine. However, it's a thankless job because it needs to be done and the higher-ups expect someone to do it.
You just better have thick skin if you take on this role. People don't like having their projects questioned and even if you understand the project you just don't understand.