It's really sad to see people (if you want to call them that) steal other peoples work. But you have to wonder how much of your art is taken from the internet and used for their own purposes.
My daughter has a lot of her stuff up on Deviant Art (she is quite good at Photoshop) and imagine her surprise when one of her fans in Germany (we live in the US) sent congratulations on her art that made it on a book cover, she never gave any permission to use it. After she did some investigation she found a past post (she thought was spam, my wife and I also felt it was) on Deviant Art that wanted to use her art and they wanted her Bank Account number - she never replied to this person. This post was unprofessionally written and they didn't explain who they were. So to make a long story shorter they are German ad agency and the book was published by Random House of Germany, we went to a copyright attorney and he agreed to take the case and in the end my Daughter won her case, they tried to blow it off as a misunderstanding, I don't think so.
Since then she has been placing watermarks on her work and keeping the resolution down.
The reason I decided to post this was to give you another angle to keep a eye on, keep checking those book covers!
Great job guys!
Glen