I used essentially this method as well for personas (personas.media.mit.edu) as so many web results were the same... except I kept track of duplicates to then employ further metrics to select 'the best one.'
Do you really think they have a blind suspicion of everyone? The vast majority will go through with minimal questioning, and these types of questions try to tease out suspicious behavior. I don't think it's a "you are guilty by default" type situation.
How would you rather the border patrol act? Keep in mind there are various types of illicit behavior that are not desired within society--this is a fairly inevasive method all things considered.