From [http://www.harvardnsj.com/2010/04/cybersecurity-and-national-policy/]:
Those with either an engineering or management background are aware that one cannot optimize everything at once — that requirements are balanced by constraints. I am not aware of another domain where this is as true as it is in cybersecurity and the question of a policy response to cyber insecurity at the national level. In engineering, this is said as “Fast, Cheap, Reliable: Choose Two”. In the public policy arena, we must first remember the definition of a free country: a place where that which is not forbidden is permitted. As we consider the pursuit of cybersecurity, we will return to that idea time and time again; I believe that we are now faced with “Freedom, Security, Convenience: Choose Two”.