There's an interesting article on BBC about how dirty keyboards actually are. Quoting the article, "Out of 33 keyboards swabbed, four were regarded as a potential health hazard and one harboured five times more germs than one of the office's toilet seats."

Next time, think twice before eating at your workstation and as the article recommends, clean your keyboard regularly.

More information:
BBC News - Keyboards 'dirtier than a toilet'