To Patch or Spot?, Wait for it to break or stop it from breaking? Options

[Socinus]

In a game, some people take the approach that it must be balanced and break-proof before play starts. The GM will systematically go through and remove game options that he/she feels are broken and parts that a player could use to break the game. Others will take a more laissez-faire approach and leave most of the game alone aside from one or two glaring problems **coughslowcough** and trust that their players wont break the game even though they have the ability and knowledge to do so.

Which approach do you prefer as a GM and as a player and why?