Apple admitted that "some MacBooks may have left the factory with a thin piece of clear plastic covering the rear vent". If your sparkling new MacBook is overly warm laptops and / or has constant fan operation then check if you have a thin plastic covering the vent. The solution is simpler than you think.

Apple says: "If your MacBook has the plastic still over the vent, simply remove and discard it."
via Reghardware

Ain't that simple? I only wish Apple would be more careful the next time around. Few more of such "scratchable iPod nano" incidents and even Apple can lose credibility on quality.