My husband and I don't have the same last name and we've never had a problem going through the line together. Although I carry our marriage license just in case.

Along a related line of questioning, on a recent flight to the US we were told that we'd have to fill out separate customs declarations (even though we were married and obviously live in the same household) because we have different last names. I've never had this happen before and never heard of it. Anyone know of any recent rule changes? We didn't have a problem at customs. But I thought it was curious that the flight attendant thought it would be necessary. But perhaps she thought we weren't married.