In response to the person who said even if the head touches the MD it'll just scratch it: MDs use lasers, not magnetic heads like in hard drives. In order for the laser assembly to touch the MD, it would have to break off from the base and fly straight up. In other words, you'd have to almost run over the MD player for that to happen.
In response to the post about dropping HDs instantly or inevitably killing them: I know people who have iPods and have dropped them several times on hard ground and they have survived the impact. Apple and other portable HD players have enough engineering background that they can minimize the shock to the HD. Of course, a MD player is still much more durable than an iPod, but HD based players aren't as prone to shock as people believe them to be.