I used to think that, and then I was "that guy." I didn't leave it at security but actually left it on the plane. Was traveling with my fiancee and her 4-year-old son, it was fairly chaotic and I managed to leave it in the seat back pocket. I didn't realize it until an hour or more later during our layover when I was going to look something up on it. It was a VERY sickening feeling to realize what had happened. At that point, that airplane had already departed for another destination.
Thanks to some exceptionally helpful people at AirTran (now a part of Southwest) and company ID stickers that are on all our laptops, it was found at the next destination and they FedEx'd it back to me at no cost.