I carry my laptop in a Cortech tail bag. Mostly because I prefer the comfort of not having 10 pounds of shit on my back. I've heard plenty of intelligent people say that the vibrations are bad for the hard drive, but something like 25-35% of new drives die within their warranty period under normal use, so it's not like I'm destabilizing something that was super stable to begin with. I backup work stuff at work, and run a backup script nightly. I figure the hard drive is sacrificial anyhow. If I stack (and still have use of my eyes and fingers) it'll be a good excuse to buy a new laptop.
At the end of the day, the data is far more important than the laptop anyhow, and I've always got that backed up.