One case study from the Committee on Publication Ethics (COPE) website (http://publicationethics.org/case/what-constitutes-authorship):  

Author X submitted a paper to another journal, and included author Y, a student in the same institute, as a courtesy. Author Y had drawn two figures for the paper and discussed some of the observations (all made by author X) with author X but the paper did not deal with the thesis research of author Y.

After the original paper was returned, requiring extensive revisions, author X revised the paper and submitted it to our journal. Author X did not include author Y as an author, but listed Y’s contribution in the acknowledgments. Following notification of acceptance and online publication, author Y complained to the editor, insisting that he should be added as an author by the journal without reference to author X. The editor contacted author X who indicated that author Y did not make a substantial scientific contribution to the article and that the notice in the acknowledgments was appropriate.

Authors X and Y hold similar views as to what author Y’s contribution was, but different views on whether this is sufficient for authorship. The editor notified authors X, Y and the administrative head of the institute, and recommended that the parties resolve the matter among themselves. Author Y indicated that this suggested approach was unacceptable, repeated that he should be added as an author on the paper regardless of the opinion of author X and did not accept the editor’s position that this matter could not be resolved arbitrarily in author Y’s favour by the editor or the publisher. Author X has insisted on publication as the single author. The editor has continued to attempt to make contact with the parties, without recent success.

Advice from the Committee on Publication Ethics (COPE):

The Forum noted that the editor cannot determine the intellectual contribution of the authors. The editor needs to contact the institution again and obtain a clear ruling on the case. The advice was to pursue the case through the institution and inform the authors of this. For the future, the editor should look at the author guidelines of the journal to try to ensure this situation does not occur again. Permission to publish should be obtained from all authors on submission of the paper for publication.