Great article. Tons of good information in that one. I think the major difference between a BDSM relationship and an abusive relationship is that in a BDSM relationship the control is given voluntarily and within agreed limits whereas in abusive relationships there are no limits and the control is forcefully taken from you. (This is from a submissive point of view)

In general, listen to your feelings. If you feel that something is wrong, something is most definitely wrong. This is simplifying a complex matter though (I myself learned only after almost 3 years that "only sometimes" to the question whether I was afraid of my partner was not SUCH a good answer...) that's why I think that it is so important for everybody to be aware, and at least know a little bit about the red flags.