In today’s Age newspaper was this article:
LAPTOP computers may be damaging male fertility because they overheat men's scrotums, new research suggests.

If you are going to use a laptop, you really want to invest in a lap desk.

“Why?”, you ask?

Well apart from the risk of cooking your scrotum*, there is also the risk of third degree burns, and “toasted” skin.  A quick Google for laptop desks, turns up these:
Lazy Laptop stand logitech lap desk

(click on the pictures to be taken to the vendor’s websites)

* – when I was a pimply faced youth, I learnt in a sex education teacher that a hot bath was effective in killing sperm.  Seems now that a quick 30 min session of World of Warcraft will do just as well…