I've been a member of dA for about 7 years now (I deleted my old account and created this one, in case you wonder) and the last few years I noticed a development, which I'm not sure of if it's a good or bad thing.
Of course, art-thievery is a really bad thing. And normally, it's something you can be dragged to court for, since it's a real crime against copyright-law. And besides that, it hurts the original artists. Some may think "Oh c'mon, it's only a picture... Not even printed out!", but let me tell you, it isn't. It's work. It's a part of the artist's soul and mind. Often, it's something very private and the artists put their hearts into their works. All this is stolen by art-thievery, not only a picture.
It is good to see, that people are aware of this and try to stop art-thievery by reporting obvious copy-cats and chronic art-thieves. The phenomenon of this kind of crime seems to have increased within the last few years, but so has the number of people that are fighting against it. That's good, I think.
Another thing seems to have increased as well.
All the reports, journals, comments etc. that deal with this issue seem to make people paranoid. I often read comments below pictures, that cried "Art thief!!111!!" without any proof. Or comments of people doubting the originality of a picture, only because of slight, hard-to-be-seen similarities to another picture of another artist. It feels as if a kind of witch-hunt has started, where everybody doubts everybody to be an art-thief.
And all those people seem to forget, that public falce accusation also is a crime and deeply hurts people. And it's not done with a simple apology.
Imagine, you accuse someone of commiting a crime in the real world, and you're wrong. If it comes out, that you falsely accused someone of that crime, you get punished. Because this also is a crime (at least here in Germany).
It's the same with the issue of accusing someone of art-thievery, who is innocent. I don't know, how people can just forget or not know this. Maybe it's because they think in the internet, they're anonymus (which you aren't at all, believe me).
What I want to say is:
If you think, someone has stolen a picture or didn't credit the work he/she referenced from, FIRST search for proof. If you don't have any proof, every accusation is worthless. If you are lucky to find solid proof, you can tell them, they shall take down the picture and REPORT THEM in any case. If you don't find solid proof, approach the person with a note first. Don't just shout "Art thief!" or "This is stolen!" or something like that into their comments. Try to contact them and first friendly ask and tell them about your doubts. I think, the innocent ones will not mind proving that they are the original artists, if you friendly ask them about it.
So why do I write all that stuff?
Because that false-accusation-thing happened to me just a few days ago. I was accused of not having credited a picture the person believed me to have referenced from. Which I didn't.
Maybe you think I'm overreacting or exaggerating. But when it comes to my pictures, to my work, I don't know friend nor enemy. I enrage and fight like a lioness, defending her cubs. Because all of my drawings are a part of my soul. I may not be super-talented and also I am almost completely unknown here, but I put all my heart into my works and every picture is like a child to me. They are mine, and I show no mercy, when defending them.
This may sound harsh and pretty hard, but if you are an artist, you know what I mean.