Why are "premium" laptop vendors still putting vents on the bottom of their machines? Did they never try actually putting their laptop on their laps and realise how much that design sucks?
While it is possible to use a notebook on your lap, you are not supposed to. It is a terrible place that is unergonomic. You are supposed to put them on a table of some sort. If you are using it for more than something quick you should have a separate keyboard and mouse (ie attached to a docking station on your desk). The portable form factor is useful for meetings, presentations, or other such - but for real work they are terrible.
Since the lap what it was designed for, and a lap is a bad idea anyway: putting vents on the bottom isn't bad.