I don't think it is necessarily always due to their perception of you, I think it is also if they just feel like being a jerk. My second international return, I was sent to secondary for 2 hrs. I think I was 24 at the time, mid-January, coming in from about 3 weeks gone. Flew coach on VS, nothing out of the ordinary. One mistake I made was that I put "student" for occupation, which was absolutely true. Now, I don't care what I am studying, I won't put student on *anything* from any country. Oddly enough, I have had few or no problems with US customs since then. Knock on wood. Also oddly enough, the one place I *always* have problems is going in and out of Indonesia.