I had an interesting experience, during the boarding process on flight to Mexico. CBP/Customs officers were checking passports and asking questions. I was pulled aside for additional screening to my belongings. laptop and personal belonging. The CBP/Officer was very polite and professional but I felt very uncomfortable with all the questions, since I had nothing to hide I answered all of them. I hold a US passport, I am naturalized. How much money I was carrying?, business/pleasure travel?, where do you work?....etc. Even how many days I was planning to spend in Mexico and how many times I had used my US passport, also since he found passport page stamped from a previous visit to another country he politely asked If I liked that country, I said I loved it my spouse is from there. Then he proceeded to wrote down in a piece of paper (blank back side of Customs flyer, not a form) my passport number, name, date of birth and the numbers of days I will spend outside of US and let me go. I can understand the screening but all those questions ? and writing all that personal info on a piece of paper. Is this legal?? Should I prepare myself for a deep screening on my return?? Again never been in trouble, zero. Not the first time traveling but first thing going through this. Also I am concerned that he wrote all that info just on a plain piece of paper.