"I recall going through security at the Charlotte, NC airport once, a few years ago, and noticed TSA agents out in the queue making smalltalk with all of the passengers. "Hey, how are y'all doin' today?", "Goin' someplace warm?", "Be sure to take off that belt buckle sir.", "Were are y'all headed?", "Y'all fly much?", and so forth. At first I thought that this was a misguided effort at public relations. But then it occurred to me that those agents were probably pre-screeners looking for nervous and evasive passengers who would then be subjected to additional traditional screening. I don't know what SPOT is and have no opinion of its effectiveness. But it seems to me that chatting up passengers in order to spot potential trouble-makers is probably the single most effective part of the whole TSA process."