"The internet—not to mention culture in general—is, of course, a gigantic copy machine and that which is posted will be copied. As always, I emphasize that reactions to a plagiarism (imagined or real) are always more interesting and tell you more about the parties involved than the plagiarism itself."
Austin Kleon - in response to Banksy not a plagiarist, just careless
And this, I think, is the bottom line. It's simply human nature to want to possess what intrigues us, catches our eye. For many that "possession" takes the form of a challenge, to figure out how the thing came to be, to see if we too can reproduce it. In my case, I almost always wanted to put my own twist on it, if it were something having to do with textiles. If it was not textile oriented, then my thought would be, how can I get the same effect in my chosen medium? Copying is a form of flattery, although those being copied don't always see it that way, nor desire it. Take the case of Hannah Headlee.
Hannah was a contemporary of Rose Kretsinger, famous 1930's applique quilter, teacher & pattern designer from Emporia, Kansas. Hannah's training was in china painting, but her acquaintance with Rose got her interested in quilting. She used Rose's designs as inspiration but never copied them, preferring to come up with her own original designs. My favorite of the few she made is Cranes, which looks nothing like the sort of applique quilts being designed at the time. (See this quilt and others by Hannah on Barbara Brackman's blog post here).
One would think Hannah would want to show off her beautiful creations, share her artistry. Isn't that what most of us want to do with our quilt creations? Isn't this why we enter quilt shows, take part in exhibits? Not Hannah. Instead, Hannah refused to let any of her quilts be shown publicly because she knew what would happen as soon as she did. Someone might use her designs and she did not want to be copied. Ironically, since the rediscovery of her quilts by family in the 1980's, at least one of her quilts had been patterned and images of her quilts have been published in magazines, books and now on the internet.
So I suppose the lesson is, if you are concerned about being copied, plagiarized and the like, then you must keep your work to yourself. To which I would say, then what's the point?