I think there is a certain portion of folks interested in the paranormal who automatically dismiss anything to do with orbs. Sure, when dust particles appear on film, they can mimic orbs, but when they appear to be glowing, or they're especially large, I don't believe those are merely dust. I have known several very credible people who have said they have seen orbs with the naked eye. I've never had the experience myself, but I have no doubt the phenomenon exist.