Some people get really hung up on thank-you cards . Plenty of folks place a high value on gift-giving, and for some reason, they are also very insistent on receiving a thank-you note. Thanking the gift-giver as you open their present should be enough, right? When you can look the person in the eyes and genuinely appreciate their thoughtfulness and chat about the gift, that seems like it should be sufficient. But some people believe that if you don't send a physical thank-you card as soon as pos…