alt Hacker NewsThere actually is a law of conservation of mass (it's the same law, because mass is energy) and it only appears violated if you forget about the particles that are zooming away at the speed of light. Of course the mass of a system changes if mass can flow in and out.
Mass is not the same as energy. Mass can be converted to energy or has energy, but a photon, for example, is massless while carrying energy.