1) Trading cocaine sounds good - target Civs corruption levels go through the roof as you get their people hooked and they turn to crime to feed their habit, target Civ starts to hate you (unless target Civ is the UK, government here wants to legalise all the drugs - guess they drooling at the potential tax revenue or something
) Anyway, it would add another element to the game.
2) New resources are found all the time - theres only 30 years supply of oil left right now, and there was only 30 years supply left in the 1960's
, so I think resources still should be discovered elsewhere
3) What Sean said