Tim Harford warns against bad data in science:
Some frauds seem comical. In the 1970s, a researcher named William Summerlin claimed to have found a way to prevent skin grafts from being rejected by the recipient. He demonstrated his results by showing a white mouse with a dark patch of fur, apparently a graft from a black mouse. It transpired that the dark patch had been coloured with a felt-tip pen. Yet academic fraud is no joke.