Well, here's my two cents on this whole thing.
It is one thing if someone claims an art piece to be theirs. However, what harm comes from it than annoying the artist and/or the person's copyrighted character?
In my opinion, the real crime is when the "theif" makes a profit on someone else's work. If someone uses one of my pics, oh well, they should've asked, but no harm really done. But if they sell it or make some kinda money off of it without my permission, I wanna piece o' the pie, darn it! That, I think, should be the basis of any kind of lawsuit.