you can read on the internet about lots of different laptops that get can get hot, Macbooks are just one of them. I would place the laptop on something that can act as a heatsink (not a heat insulator!), or even get some kind of laptop cooler for the Macbook.
Traditionally you would do this kind of number crunching work (that's really what it is) on a desktop which would hopefully be designed to handle the heat from the CPU or the HD. More and more folks are shunning a good workstation and trying to do everything on a laptop or even a netbook or tablet. But for heavy duty tasks a good workstation-type machine is best.
The new intel chips that are in the Macbooks and now iMacs can really outperform most older desktops, it is that big of a change, and the new chips excel at media operations, and anything really. I think now laptops can be too powerful for their ability to keep themselves cool. The chips are running cooler yet they can do more work than ever, but the laptops manufacturers are just not focusing on heat issues. It cramps the style...even a solid aluminum body may get to hot for comfort.
Can you do so much work that you can fry an egg on a laptop - easily.