The only time I have taken part in glomp circles was when I knew everyone there. It's not a case of not liking the unfamiliar, it was more along the lines of making myself more open to trying it. It's not the type of thing I'd start doing just to do it, plus I'd worried about who well my back would hold up. The only time my back felt in jeopardy was when a girl practically leaped into my face, (and yes, if you're wondering, her breasts were about an inch from my face, though I don't think it was intentional). The quick shift of weight wasn't too generous to my spine. If the circle has rules structured to protect those who feel uncomfortable about these issues, both yours & mine, then there's nothing wrong with them.