I taught knitting. One of the students had her friend drive her to the class. The friend then sat through the class, although she had no supplies and didn't participate. At the end of the class I was checking out the student who purchased additional supplies. Then I asked the friend if she wanted to purchase the pattern (my design). She said, "No, I'll just copy Susie's." So I said, "Then I'll just charge you for the class." Had she bought the pattern I wouldn't have charged her for the class but the comment about copying the pattern was too much.
I did have a number of positive experiences. My favorite was the young woman who was unsure of herself in the beginning but ended up knitting a beautiful vest for her mother. None of her siblings would believe she did it until she pointed out there was no label. It made her so proud because she told me she'd always been the one in the family who nobody thought could do anything. I think she gained a lot of confidence from what she accomplished in my class.