The advantage of using barcode technology is that it is cheap and easy to generate the credential and it can easily be applied to cards or other items. However the same affordability and simplicity makes the technology susceptible to fraud, because fake barcodes can also be created cheaply and easily, for example by photocopying real ones. One attempt to reduce fraud is to print the barcode using carbon-based ink, and then cover the bar code with a dark red overlay. The barcode can then be read with an optical reader tuned to the infrared spectrum, but can not easily be copied by a copy machine. This does not address the ease with which barcode numbers can be generated from a computer using almost any printer.
In 1958, the English-born Spiritualist C. Dorreen Phillips wrote of her experiences with a medium at Camp Chesterfield, Indiana: "In Rev. James Laughton's séances there are many Indians. They are very noisy and appear to have great power. [...] The little guides, or doorkeepers, are usually Indian boys and girls [who act] as messengers who help to locate the spirit friends who wish to speak with you."[20]
Then I got a call from “Denise,” wanting to know if she is going to get enough money from the insurance company for being rear-ended because she needs the money desperately. I wanted to say, “In that case, hang up the phone!” as well as explain to her that I was an expert on love, not claims adjustment. I laid out the cards anyway. I realized I really didn’t want to give this woman advice, so I hemmed and hawed, and she let her time run out at five minutes.

Jean Pierre Allaire was counselling a 13-year old Trois Rivieres girl who reported seeing people that others could not.  He told the girl she should go to the medium to find out whether she has a psychic gift.  He also told her not to tell her psychiatrist about what she was seeing and hearing because that might lead to an increase in the anti-psychotic medications she was taking, which were making her sleepy.  
In 1988, the magician Bob Couttie criticized the paranormal author Brian Inglis for deliberately ignoring evidence of fraud in mediumship. Couttie wrote Inglis had not familiarized himself with magician techniques.[178] In 1990 the researcher Gordon Stein discovered that the levitation photograph of the medium Carmine Mirabelli was fraudulent. The photograph was a trick as there were signs of chemical retouching under Mirabelli's feet. The retouching showed that Mirabelli was not levitating but was standing on a ladder which was erased from the photograph.[179]
Some scientists of the period who investigated spiritualism also became converts. They included chemist Robert Hare, physicist William Crookes (1832–1919) and evolutionary biologist Alfred Russel Wallace (1823–1913).[13][14] Nobel laureate Pierre Curie took a very serious scientific interest in the work of medium Eusapia Palladino.[15] Other prominent adherents included journalist and pacifist William T. Stead (1849–1912)[16] and physician and author Arthur Conan Doyle (1859–1930).[17]