No matter how careful you are about physically protecting your small notebook computer, you need to plan for the worse. A few months ago, The Unofficial Apple Weblog (TUAW) had an article 9 things I learned from almost losing my MacBook Air. It is Mac-specific in the details, but no matter whether you have a MacBook, a Windows notebook, or something else, computers are getting smaller, disks are getting larger, and that raises the vulnerability to information loss. And no matter what you think, you have data on your computer that, in the wrong hands, could cost you money.
It reminded me of a few columns, not Mac-specific, I wrote years a few years back: