I rarely do but sometimes it's because I don't have time to run out and buy something and it's for a cheesy game at a party to exchange gifts and not for someone important like close family.
As a rule I'd only regift something as a serious gift if I really thought the person would appreciate it, and if I hadn't used it in the meantime. Most of the gifts I exchange with people are token gifts rather than having either of us stressing over what to get and how much to spend, and where token gifts are concerned I have no problem regifting.
Sometimes if someone gives me a really silly gift I'll get them back a year or two later by giving them the exact same item back, wrapped creatively so it's not obvious what it is
