I think thank you notes are highly overrated BUT I think a thank you of some form is in order. We went to a relative's wedding and brought a nice gift - never heard a thing. Made us think that we were only invited for the gift value (Actually, I think I drank enough to cover the expense, lol) Next invite we declined and have not been bothered again. I love it when someone either opens the gift right away and I see their reaction or calls me after the fact and we chat for a bit.