Beware of coming in to the U.S. with more cigarettes etc or money than you should have. Arriving last week I had $13k on me and my friend had $6k. We had never ever been asked before how much money we had and just ticked the customs form as we had less than the 10k each you should declare. When asked we told the truth and because I was carrying more than the 10k on my person our cards were marked with a 'C'. We were told it was fine and he had put us down as being together. However we got to the exit where you have to hand your card in and were told to go to the other room. The queue was huge, about 70 people and only two staff members to start with. A few Mexicans in front of us from the previous flight and then all BA customers. Most BA customers had duty free bags and had over 200 cigarettes per person. One guy had a carry on bag and seemed very nervous. They were checking all duty free and stopping everyone that had more than the allowance. I've never seen them be so thorough before, especially never been asked how much money we have. There seemed to be way more people being stopped this time. I can't imagine that somehow they can find out how much duty free you buy at Departure airports when you have to show your boarding pass but it sure has made me wonder if they have access to that information. It took us just under an hour and a half in that queue and had a form to fill in. The guy was extremely nice and only doing his job but thought I'd give everyone a heads up. Even if you travel as husband and wife ensure one person doesn't carry more than 10k USD. It sure isn't worth the possible hassle. The fact you can take it in isn't the problem, it's the queuing to fill the form out and delaying the holiday. Very impressed with BA though, they had a member of staff there in that room until the last passenger had been seen in case they needed to help anyone. Impressive.