I've had three apple laptops, the last two Powerbooks in the aluminum case (which I had thought to aid in temp control).
The problem is that I was constantly running the chip to 105C, which is way beyond the correct operating temp for long term life of a computer and its components.
I've never recorded my tower going over 58C, and it normally runs at 45-48C on a full load with all 6/12 cores running 80%+.
Not to say that all laptops will do this, but it's a lot of power consumption for such a tight area, physics applies.