As a flight attendant I have had it happen more than a few times since I work primarily transcons. The first time a woman plops her self down during the first beverage service, I ask if I can help her, she says "get me a bloody mary", I say "get me your boarding pass" she says "I can't find it", I get the manifest and ask her name, now she knows she's busted and gets all defensive, starts spewing the "I work for Gillette and do you know how much money my company spends on this airline", I replied "I have been shaving since I was 16 and never recieved a free razor so either you can give me your credit card, move back to your seat or the captain will have the authorities at the gate to meet you." She didn't like that and wanted my name, I wrote down my name, supervisors name, phone number, the number for consumer affairs and told her to have at it. She picked up all her crap in a huff and moved back to coach, the rest of first class gave her an ovation as she left which really pissed her off.
One other time that stands out was during boarding on a 767, myself and another flight attendant were standing behind the bulkhead seperating biz from the lav and heard this lady say "let's just sit here, they'll never know", right away the other girl starts to head out to nab them, I grab her and tell her it's time to have a little fun, we go out of our way to show them biz service, the predepartures, menus and how the best part of the flight is the warm cookies and milk before landing, they are practically salivating at this point. Finally the door closes and we go get our copy of the manifest and make a big prodction of doing the head count, we do it about 3 times while pointing while we count heads, we ask a couple of the people to see their boarding passes and then head to the ploppers, when they show us their boarding passes we tell them "Oh, these are not your seats, you are in the back of the plane, please take your bags with you." Once again the real biz folks got a howl out of it and made it a fun flight for all of us.
So beware if you are on one of my flights, I always count in premium cabins, LOL.
Mike-BOS