Automated Southwest check-in
I only mention this because it's the second time it's happened to me twice in exactly the same way:
I was flying out of Oakland airport yesterday on Southwest. My reservation was for a 6:30 PM flight, but our meeting finished early, so I had my assistant call Southwest and change myself and a business associate to a different flight. We arrived at the airport, I went to the automated check-in kiosk, swiped my card, and was told to go to customer service. MY business associate swiped his card and received his boarding pass.
I went to customer service, got my boarding pass by showing my ID (yes, I was on the earlier flight), but the pass printed with the fabulous "SSSSS" designator (for those who may not know, the multiple S designator means an automatic trip to the secondary screening -- take off your shows, get wanded after walking through the hood, and have all of your carryon baggage opened and hand inspected). Yesterday, secondary screening actually wound up being the express lane -- I went through faster than my colleague.
Just out of curiosity, I went back and checked, and found that I had switched my flights in the exact same way almost a month ago, leading to exactly the same result.
Interesting coincidence -- I'm going to try it again the next time I'm there.