This seems to be a contentious issue, but my take is that I see no inherent wrong in it. In advance, this post may seem tl;dr, however there are a number of points I wish to convey.
Some equate it to a doctor/patient relationship, but personally I don’t see how this is so. As a doctor cures/manages illness, then obviously ethical practice and good judgement can be compromised should a doctor and patient be friends or more. Also, medicine is obviously a case of life and death in numerous cases. In contemporary society at least, yoga is seen largely as a means of improving fitness, and certainly not a life and death thing as medicine. This may detract from how yoga was envisioned thousands of years ago, but societies and norms change over time and per place.
Also, I would have no issue attending a class in which the teacher and his or her students were friends. Provided that all students had means to approach the teacher concerning asana advice, or that modifications/adjustments were provided to all, then I see no issue. the teacher could even say at the start of the class “say hello to Tim my husband over there” and I wouldn’t mind. Provided the teacher didn’t only offer adjustments to “Tim”, then again it’s immaterial as I see it. I would say in general, people leave yoga classes if they feel uncomfortable, for whatever reason.
On this general topic though, I am a new yogi, since I started about a year ago. I go to a studio about 5 miles away from me, and attend a class run by a 30 year old woman. I had to have a hiatus, due to work commitments, but left some messages on her Facebook page regarding her classes. She added me as a friend there, and said she missed me in classes and wanted me to come back. When I did return (as work tasks eased) she welcomed me warmly and said it was good to see me again.
I’m a bit confused of her intentions though. I know that everybody is different, but is she just happy to see a familiar face in class, or does she want to be friends? Per the points above, I don’t see an issue with it, however I don’t get what she is about here.
Thanks.