If I copy an image I see on Pinterest and the artist's name is unknown, whom do I credit? Most of these images appear on many pinboards and no attribution is given to the original artist.
Very good point! I was wondering about just the same 
Or something like e.g. quilted cookies, needlepoint, ... - there are so many of them, how is one to find out who was the first?
I generally absolutely agree with this topic, but I suppose that a lot of cookies are very similar because it is the same design ideas which are used again and again (flowers, shabby shic, cute little bunnies, flowers again, etc.). Also on this side I see so many cookies which I can hardly tell apart - and that still doesn't necessarily mean that people are infringing.
Or how about all the Frozen Cookies? Is the movie name enough or should Disney be added?
I habe to admit, I am puzzled...