From the teacher's point of view, it is very difficult when there are "know it alls" or extremely needy people in the group. I used to teach hand applique at a couple of quilt shops, and it was a lot of fun when everyone participated and was supportive of everyone else. The last time I taught one person hogged the show - kept interrupting, wanted my attention all the time, didn't allow others to speak, etc. It was exhausting and not worth the money I made (and spent right away at the shop!).
I belong to a small group that gets together monthly to hand sew, knit, embroider, etc. We all help each other and share tips and ideas. It's a lot less stressful and we learn from each other more informally.