Polygraphs are shaky areas. They involve alot of "grey area." Without going into much detail, they don't look for lying or not lying, they look for deviations and highly rely on physiological factors. I have taken more than one and both passed and didn't pass. Its stupid to call it fail, because its not really failing. Sometimes they just can't get a good read on you for certain questions. If that is the case, then they can't hire you. The CIA uses a lifestyle polygraph that is much more in depth than many other ones. However, it doesn't mean *&^% in the grand scheme of things. Its not like the results can haunt you from other employment, unless of course you didn't disclose being a drug dealer or a terrorist.