During my last visit to the USA, just before I was boarding my flight at the gate on the way BACK to the UK via Germany. Right as the gate agent scans your ticket and lets you walk down the jetway to the plane, there was a CBP officer taking everybody's passports and asking them their purpose of travel to the USA and how long were they there for in a pretty relaxed and casual fashion.
I had an old J1 visa in my passport from two years ago and he quickly stated it was out of date and I should have had an ESTA to travel to the USA. Once I explained the J1 was an old visa and I wasn't travelling on it, he gave me my passport back and moved along.
Has anybody experienced this sort of thing before? I go to the USA about five or six times a year and this has only happened once on my latest trip - a CBP officer asking me my purpose of travel to the States when I'm leaving the country.
This was at the North Terminal at Detroit airport (DTW), at what I believe was gate D3. I was flying back on Lufthansa A340-600 aircraft.