[scottLobster]

You have to define "they". One of the most useful aspects of polygraphs is their ability to spur spontaneous confessions. Most people who leak/serve as foreign agents are not Snowdens, they're largely weak people who's weakness is being exploited by a geopolitical adversary. Put a weak, vulnerable person under the microscope, present even a hint of extra scrutiny and all the consequences that might entail, and they often crack out of semi-irrational fear. I say semi-irrational because while ploygraphs don't often hold up in court, they can be useful in targeting potential suspects for further investigation/monitoring.

It's not all jail cells and Guantanamo bay.