Yes, Marbury v Madison established that the judiciary could deem a law unconstitutional. It is true the founding fathers made the judiciary rather weak (whether by intent or just by happenstance I don't know. maybe they just didn't have much practice at the whole government-making game and failed to adequately outline the powers of the judiciary.) Anyway, John Jay was the first Chief Justice of the US Supreme Court and he quit basically because he thought the job was pointless and had no real power. John Marshall succeeded him and set out to make the judiciary have more defined powers. I think in general his judicial reivew and establishment of the rule of law was a very good thing for the US, although it certainly can and has been abused with suspect rulings and some judicial oversteps. Then again, the judicial branch certainly is not without peer in this sense considering the myriad executive and legislative oversteps through the years.

Anyway, the media is checked by both laws supposedly preventing mendacious reporting and by the general sense of believability. When a media source loses credibility it loses everything. I think our media is currently headed down that path and we shall see what the result is.