If a person is profiting from some else work without their permission it's wrong and illegal.
If they claim that it's their work then yes, it's wrong and unethical. (whether they profit from it or not)
If they don't give credit to the source, yeah that's lame/lazy.
That's where the discussion end.
Even if they give the source it does not give them permission to use it. They always give the source. That means nothing, it's still not legal or ethical.
I have had my work features in magazines and blogs, they always ask for permission first if they are ethical and complying with the laws.
Take a look at the photo you just stole of mine it has my copyright notice on it, and my contact info.