I have personally not had this happen to me but I saw a similar discussion on dA and thought it an interesting topic for us over here on Etsy.
A lot of us make items of games, shows, comics, etc which are licensed to the prospective companies who first produced them. Due to the nature that we are drawing inspiration from the same characters and such some people end up producing very similar or identical items. Some people who produce their own patterns do use the Creative Commons License to protect themselves somewhat from thief and copying which are stated on listings and on the items when you receive them.
However some items which do not use patterns but are items such as pillows, clothing, hats, etc I have seen write "You may not remake this item. Failure to abide by these rules will result in prosecution"
How do you feel about people who state they will prosecute you for making an item similar to them over a licensed character they do not own?