Spots 
A genuine humbug relies on clever showmanship rather than outright robbery. While a swindler takes money by force or theft, the humbug entices the public with an exaggerated spectacle or an agreeable illusion. People willingly pay for the excitement of being tricked when the deceit is mild and entertaining. True malice begins only when deception deprives victims of their health or livelihood.
Rapping spirits and floating tables depend on concealed wires, loose knots, and clever footwork rather than ghosts. Mediums exploit the grief of loved ones by turning natural sounds into messages from beyond. The Davenport brothers and Rochester knockers built lucrative careers on physical tricks that any skilled stage magician could replicate. Exposing the physical levers behind séances strips the mystery from spiritual manifestations.
Patent medicines and universal pills promise instant cures for incurable ailments without containing any effective ingredients. Quack doctors capitalize on human fear, selling sugar pills and colored water as miraculous elixirs. Victims often report temporary relief simply because they desperately believe in the cure. The real danger of medical humbug lies in diverting sick patients away from legitimate care.
Speculative manias persuade otherwise sensible citizens to invest fortunes in worthless promises. From the Dutch Tulip Mania to the South Sea Bubble, promoters inflate paper assets by promising quick riches without labor. Greed blinds investors to basic arithmetic until the panic hits and the illusion collapses. Public credulity remains the primary engine of every financial bubble.
P. T. Barnum exposes the tricks of swindlers, quacks, and spiritualists while defining the art of harmless deception.