Yep! Tons of my Stuff has been stolen and put for sale on several websites, for t-shirts, prints etc. without my permission. I am so sick and tired of people stealing it to make a profit without moving a finger. Even worse, most places edit out the signature, as if the internet is a free buffet of art you can just "discover" as steal like ancient fossils found in the ground.
So! I have taken the ultimate step and added watermarks on ALL my pictures. I'm sorry it had to come to this, but it is impossible to get people to remove my designs. The only option left is to avoid companies stealing it. It sucks a lot. My art isn't even that good, but even so - I am sure everyone with an eye for art is still able to judge my art, despite of the annoying water mark.
Not only is stealing for profit quite a problem, but the whole "upvote" culture on Reddit, Imgur and other site also enable a lot of people to re upload pictures, without crediting or linking to the original artist, just to earn 10 upvotes. Hopefully more sites will incorporate credits, such as pinterest, and help ensure the original artist's copyrights - but until then, I am tired of having previous clients contacting me, about their commission being for sale, or me randomly bumping into my own stuff while browsing the internet.
Sorry about this! I know this has a negative effect on the presentation, but what can artists do at this point, as 3rd party selling sites pop up like mushrooms these days.
At least on pages like RedBubble there is a report option.
It has come to this or deleting my DA profile, however most commissions I get are still from DA, so I chose to stay and be one of those people, slamming watermarks on everything. Sorry!