Let's say you work in a shared office environment and want to prevent someone from eavesdropping on your computer use. You take the logical precautions: you have a lock on your floppy drive, you set a password in the BIOS, you encrypt your files, and you use only secure protocols for remote interaction. Odds are still low that you have a shroud or other physical impediment preventing access to your keyboard's PS/2 port, right?
Interestingly, the KeyGhost is also available in a Microsoft Natural model, so it might be inconspicous in many settings that a new standard keyboard might stick out in. So now you have more reason than plain cynicism to wonder at an "upgrade" to your regular keyboard at work. Of course, most programmers have settled on their keyboards after long trial, and would never disregard such a switch.
Despite the obvious unscrupulous uses this keyboard could be put to, I can think of one that isn't: I'd like to see one of these drawing its power from a battery pack instead of the PS/2 port and featuring a tiny LCD display, for times when it'd be nicer to type an e-mail out on the porch than inside, or as a more efficient idea-gobbler than a pen-driven PDA.