Why? Do they use it when the laptop is closed? Did they miss a numpad? Did all their keys pop off and the devices are out of warranty? Is it about the "click" feeling?

I haven't seen this so I am curious. The biggest bummer for me about Apple is the lack of a USB external trackpad.

Is this what you're looking for? http://www.apple.com/magictrackpad/

I think gurkendoktor is looking for a USB(wired) trackpad. The Magic Trackpad can only interface via Bluetooth.

Right. BT is annoying when changing operating systems or computers and batteries are bad for the environment and always run out at the wrong time. I went with the Magic Trackpad though.

I guess it is about the click feeling and proper position of the hands.