I think it's about being tasteful. Be honest if you think they'll suspect it and take Fawn Liebowitz advice. ^^^ I have been on both sides and it's usually no big deal.
However, don't be a constant re-gifter. Mr. Fleur de Lis' grandparents are infamous for re-gifting. This year, we're getting them restaurant gift cards because they don't need any more stuff. I just KNOW they'll end up in the family gift swap.
