Dude, of course, mice get gunk on them, as do keyboards. It's pretty much a given that anything that is in constant contact with hands is going to get really dirty. I've never seen a keyboard older than a month that wasn't filthy, especially underneath. I have both the aluminum chiclet keyboard and the older plastic Apple Pro keyboard, along with a Bluetooth Mighty Mouse and wired Mighty Mouse, which I regularly unplug and clean, usually with anti-static wipes. Once and awhile I'll get the vacuum out so I can get all the crumbs from under the keys too. 😉