>>6
I prefer to make the entire memory area readable, writable and executable. That way the application can do interesting things when programming errors occur, and bugs can sometimes become features.
That being said, I don't think programs should have access to the CPU fan. It restricts my freedom if I have to worry about accidentally turning off the CPU fan and frying my computer. (No, that has never happened to me, but it will inevitably. I will then buy a new computer. I will keep breaking and buying computers until I find one that cannot be broken with software.)