Meanwhile, when governments want to check the background of someone before hiring them into a position of trust involved in national security, they'll send agents to investigate. Methods include interviewing them hooked up to a polygraph, and asking their neighbors questions face to face. All for reasons that seem to me less important then the safety of my child while alone with a babysitter.
Because a dodgy spy can cause more damage kim philby lead to the deaths of a large number of people. And its more likely that a family member is a danger to you child - than say a babysitter who got busted at 15 for smoking pot behind the bleachers with her bf.
"X is worse than Y, therefore you shouldn't worry about Y" is a fallacy.