Cube Farm Snooping
Another article from the same site as the below two articles. Anyway, seems that the proliferation of wireless devices can get you in trouble, or 'expose' your thoughts to a co-worker without you knowing it.
While it would be very unusual for an RF signal from one of these keyboards to make it 150 meters (about 500 feet for those of you who can't do metric), it wouldn't be for those stuck in a cube farm. So take care what you type at work if you have one of those devices.