I have tons of friends with kids. I typically never bought them birthday or Christmas gifts but would buy them something for a special event like Confirmation, etc. However, after the age of 18 I give them money because that's what they can use the most. If I don't receive a thank you note then they never get a gift from me again. It's easy. I write a check for $50-100 bucks and I get a note of thank you. One friend's daughter (whom I don't really know) got married and I sent her a card and check for $100 figuring a newlywed can use the money. I never heard from her but she did cash the check. A few years later she had a baby and I didn't bother. Her mother actually said something to me and I told her no note -- no more gifts. Another friend's son: same story. I'm not being mean -- I'm being fair. If I can take the time to get a card, write a check and mail it... It's rude not to acknowledge a gift with a note or even an email.