Absolute security is a myth. Most laymen would think that just because a computer device is wired that it has a higher level of security. In most cases this would be true, but in the shadowy world of corporate espionage the stakes have gone one higher. At The Security and Cryptography Laboratory (LASEC) of Ecoles Polytechniques Fédérales de Lausanne, they recently released a paper called COMPROMISING ELECTROMAGNETIC EMANATIONS OF WIRED KEYBOARDS. While this is not big news in the TEMPEST world, it is an eye opener for most businesses. The scope of keyboard technologies affected, as well as the distance that keystrokes can be read is really quite impressive.
In a nutshell: Your hard wired stuff is not safe, but it never really was. Try to mitigate your risks as much as possible and stay informed.