[Haskell-cafe] Monad laws

Hello, You guys have been great taking my questions. Thank you. Now I have another one :) What can go wrong if I make an Monad instance but don't follow Monad rules (identity and associativity)? Sure it would be misleading for someone using the non-conforming class. They may make code that assume those laws, although they don't hold. However, could it make the compiler generate bad code or some standard functions to behave badly or even break? []'s Rafael