Might move this to B&D board, but, in the meantime, this is an interesting question.
There are so many variants of bdsm relationships that there is no one answer.
-I like all my subs and clients, yet do not necessarily consider them all 'friends'.
-I became friends with some of my subs and clients, which makes our relatioships better. Am extremely close with very select persons.
-I have friends in the scene with whom I will not session, as it would change our friendship or I like our current relationship as it is and do not want to change it.
-I have scene friends who I have seen / do see for session, as it happens to enhance our relationship. Our scenes together are so enjoyable because we share more than just a kink or two.
(FWIW, I have been close friends with my massage therapist since before she became an LMT. She knows me so well, even to knowing how my mannerisms, gait, and job affect my muscles, so her massages are intuitive and amazing... and I pay her well for her amazing skills, not a single dollar less because she's my friend and I expect a deal.)
And that's how I feel about that.