I personally don't think we need to talk about self-improving AI at all to consider the problem of friendliness. I would say a viable alternative statement is "Evolution has shaped the values of human minds. Such preferences will not exist in engineered minds unless they are explicitly engineered. Human values are complex, so explicit engineering will be extremely difficult or impossible."
Self-optimization is what makes friendliness a serious problem.
I've been using something like "A self-optimizing AI would be so powerful that it will just roll over the human race unless it's programmed to not do that."
Any others?