I just got a new MacBook Pro (unibody) about a month ago. Ever since the first day I turned it on, I've noticed that all it takes is a light bump on the palm rest or even sometimes just tilting it on my lap to cause the SMS to kick in and I can hear the hard drive click as it is parked.

My old 1st gen MacBook Pro never did that unless I really got rough with it, as in almost dropping it. Is this just normal behavior on the 2nd gen models?
It doesn't interfere with the operation of the computer but I always use it in my lap and am constantly bumping it.