My hubby was a founding member of the first German BDSM association, and he tells me that the concept of "SSC" was only invented for the sake of the vanilla community. The reason for it was to point out to the vanilla folks that there IS a difference between BDSM and abuse!
He thinks it rather funny that huge parts of the BDSM crowd, especially the less experienced and new ones, are trying so hard to fit this concept of SSC.
The line is very difficult to draw - how many things have subs done for their doms that they were afraid of / did not want to do to begin with / evolved from being a hard limit to a soft limit and finally into something that was actually desired? Are these things already "not SSC"?