Stochastic Volatility Meets Mean-Variance Analysis
Wilmott does not like the market price of risk. He says so right at the start of Chapter 54, and his reasoning is solid. The market price of volatility risk is not directly observable. You can only back it out from option prices, and that only works if the people setting those prices are using the same model you are. If you refit the model a few days later and get a different answer, was the market wrong before? Or is it wrong now? You end up chasing your own tail.