I can't speak for anyone else, but my experience with a personal facebook account is that there are things I won't tolerate there, like certain types of comments. I wouldn't delete those comments or friends on a professional website or profile, but my personal profile is like my home. I choose whom and what I let in. So who knows what personal policy your therapist has. But speaking about your therapy, if this goes beyond a sense of curiosity and it bothers or unsettles you in any way (or if you just resonate with something), I suggest you bring it up in therapy. Otherwise it will be something unspoken between the two of you that will influence your therapy.