Airports are prime hunting grounds for thieves, and most savvy travelers should know better. Laptops are stolen many different ways at airports, whether it be at the security checkpoint or through the bottom of the bathroom stall while you're indisposed. Whenever I travel by airline, I use one of two alternatives to my daily Kensington laptop case. The first is a backpack made by Targus with a specially formed, padded space for a laptop and plenty of space for files and accessories. This thing has been all over the place with me, from the arctic to the tropics, and I can vouch for its versatility and anonymity.
Most folks just assume that it's another ubiquitous daypack.
This I toss into my carryon bag, rendering it invisible to onlookers. Securing your PowerBook is simple, cheap, and painless. From a cable lock to a stealth carrying case, taking to time to make sure your 'Book is safe will go a long way toward keeping you off the statistics list.