I worry far more about the "promising" stock market, particularly the "safe" blue chip stocks, than I do about speculative ventures -- the former present invisible risks, the latter offer no surprises since you know how volatile they are and can limit your downside by investing smaller amounts... I am very aggressive when I can gain exposure to positive Black Swans -- when a failure would be of small moment -- and very conservative when I am under threat from a negative Black Swan. I am very aggressive when an error in a model can benefit me, and paranoid when an error can hurt.

-- Nassim Taleb, The Black Swan