I heard about this story about Oprah Winfrey unexpectedly dropping by random wedding receptions to get footage for a future episode. I'm not a particular fan of hers, so maybe that makes a difference, but I don't think I'd be too happy if she'd done that to me. It wouldn't matter to me that she brought a nice present. Just because she's a celebrity and needs footage for a show doesn't mean that it's ok for her to just drop by the receptions of people, expecting that her celebrity would excuse what would normally be considered bad manners. And to some extent, I think it's unfair to the bride and groom to basically have their spotlights taken away.
Maybe if it was someone I actually liked, I wouldn't mind them crashing my reception. Dunno.