A second class of guest authorship is often more pernicious when commercial interests are at stake. If the paper describes products or outcomes that could influence the sales of a product, the parties benefiting commercially may feel a desire to hide the extent of their involvement in the work. Sometimes this results in guest authors, ghost authors (to be discussed below), or both. Often, a customer of the product is listed as an author (even the first author) to provide a sort of customer endorsement. I personally know of papers where customers were listed as authors even though their only contribution was to buy the product described in the paper. More frequently, however, the customer supplies access to equipment or materials and may even collect some or all of the data. But if customers’ contributions can’t be described as creative, they shouldn’t be listed as authors—it makes no difference that the goal of the project may have been to generate a “customer paper” to show off the benefits of the product. I understand that scientific papers are sometimes used as marketing tools, but their scientific value and integrity must and will be judged independent of any such considerations.