[citation][nom]CaedenV[/nom]too thin, and there are often times when the case is on fabric (clothes or blankets) where the housing would not be able to breathe and would cause overheating. Also laptops only have 1 real side to disapate heat. The top is covered by the keybaord and mouse (which would bother users if they got warm), and then the 4 sides are typically too small to have any useful cooling properties. Desktops typically sit on a flat surface, and have 5 exposed sides, so there is more opportunity to disparate heat.[/citation]
A lot of notebook users have to carry around a cooling pad with them. Since these cooling pads are about as thick as the notebook itself, I don't see why you can't already make notebooks twice as thick by substituting the cooling pad with a heatsink. Furthermore, since newer notebooks (eg.ultrabooks) can be made really thin, this would only mean there would be more space to put in bigger thicker heatsinks.
If you think about it, being placed on fabric (eg.clothes, blankets, etc) makes a stronger case for a heatsink notebook bottom. If the notebook is placed in such a way that it "would not be able to breathe", how would fans possibly be of any use in dissipating heat?
Laptops may only have 1 side for heat dissipation, but this NUC device as pictured above is really really small such that the combined 5 surfaces are probably smaller in surface area than that 1 side that laptops have for heat dissipation. To promote efficient heat dissipation, simply have the heatsink have raised fins (just like in the pictured NUC case above) so that the heatsink doesn't stick completely to table/fabric/whatever you place your notebook on.