Just yesterday I was at a function with my client company when a coworker told me she believed in ghosts; that in fact she'd just seen one in a hotel conference room weeks before, and she'd bring in the picture where she captured it. I don't mean rhetorical-device-for-my-blog yesterday, I mean for real, 24-hours-before-I-typed-this yesterday. Perhaps most intriguing is that I work in a high tech industry and the person who told me this is a bright, very hard-working person who I respect and who has a technical degree.
"Come on, [name redacted], are you kidding me? You're a scientist [name redacted]!" She seemed a little less sure when I pressed her. She asked me if I believed in anything else, like ghosts or religion (interesting that she made that connection), and I said no.
Some would say that I'm a jerk for not letting it go, but this is different than a salesperson telling a story about the big trout that got away. Trout exist; and ask yourself, if she'd announced she'd seen a gremlin on the flight home and a leprechaun in the bathroom, why would that be any less ridiculous? Because the majority is always sane? I did my best, as I always do in these situations, to make my question the beginning of a conversation, rather than the end of one (this is tricky, I know).
Technically, you can be an atheist and still believe in ghosts, though I've never met anyone in this category - as an aside, I've had many interesting conversations of what can only be termed alternative theology, as compared to alternative history. Instead of what-if Lee had won at Gettysburg, it's what-if there are no gods but there is an afterlife. There's also reverse re-paradigming. We often see science fiction movies explaining mythological phenomena of the past in terms we recognized as scientific or materialist; case in point, ghosts and werewolves in the second Matrix flick were really undeleted programs, dragons are remnant dinosaurs, angels are aliens in disguise. How about in reverse? Young Earth creationists are right and God is tricking us with light on the way from the Andromeda Galaxy; Nick Bostrom's argument shows that we're really in a temporary illusory world created to test us. Et cetera. Sorry for the digression, but they're great skeptic's exercises.
True enough, most atheists wisely spend more time worrying about the impact of politically aggressive organized religion on public life. There's a spectrum of silliness. On the far end you have unicorns - nobody believes in them any more(not after adolescence anyway); then ghosts, that make a few people needlessly afraid but have no harm beyond that; then psychics, constantly bilking vulnerable people out of money and exploiting memories of the deceased for monetary gain; and finally, organized religion as we know it, that not only takes your money, but sometimes kills you if you don't mouth its platitudes. Sylvia Browne with a crusader sword.
Psychics and other charlatans that might actually cause someone else harm are worth watching out for. Fortunately they get caught sometimes. Penn and Teller have joined a long tradition of magicians who can't stand their fellow performers becoming charlatans and passing themselves off as actually performing magic. James Randi does similar work - check out his educational foundation on the right side of the page - you may have to scroll to see the list of links. Oddly - or not - psychics and televangelists operate in much the same way and employ many of the same performance tricks.
Of course, psychic scammers aren't quite as bad as large and well-connected groups that try to stop the distribution of cancer vaccines, but psychics are still worse than people who believe in unicorns or ghosts. At least unicornians and ghostists keep their silliness to themselves, and as long as it neither picks our pockets nor breaks our legs, it's my (or your) job to decide what someone else can believe.
I'll close with a really funny but really offensive clip of a prank call by crass but powerful atheist Howard Stern (or at least one of his writers) to a televangelist and a psychic. Whatever you think of the guy, he's holding these scammers' feet to the fire. Not work safe. Total potty humor. And you'll laugh.