The S&M article could use some updating.
Having worked with professional dommes, and interacted with the S&M (now more commonly referred to as BDSM) community, much of the information provided in the article is either outdated and/or not entirely comprehensive.
As an example of the change that S&M has gone through since 1982, (when the article was written), it is now more commonly referred to as BDSM within the practicing community because BDSM, (bondage/discipline, domination/submission, sadism/masochism), is more descriptive of the lifetsyle. It is also undergoing reexamination in psychiatry where sadism and masochism, which are listed as paraphilias in the DSM-IV, now have professionals in the field arguing for their removal as pathologies due to research indicating most BDSM practiioners are otherwise mentally healthy and functional individuals.
I would recommend reading articles about BDSM and related research by Charles Moser, as well as by Alison, L., Nordling, N., Sandnabba, N. K., & Santtila, P. collectively.