Sometimes it bothers me when a person says something that makes me feel warm, or makes me laugh, or makes me take a good look at myself or a good look at the world, and then makes no effort to cite where the quote came from, leaving me to believe that the person who said it thought it up.
Just the other day, I was watching a movie I had never seen and I heard a phrase that I had definitely heard before (several times). I had previously believed that the quote I heard originally came from my friend, but instead it came from this great movie.
I'm not talking about just any quote or common phrase, but I'm talking about sayings or phrases that are used by someone to make another person feel something, to inspire someone, or to make someone think. When someone has caused me to do these or any other things as a result of something they said, and then does nothing to give credit where it is due, I get angry.
I don't become an outraged maniac or anything, but I do get upset. I feel like I have been lied to. Someone said something very insightful to me, and I respected them for that insight, but then I find out it isn't even their own! It's lying by omission. By leaving out the source of the material, you are in fact lying. I respect a person who will acknowledge the original source, or at least make an attempt to, more than a person who tries to pass off someone else's thoughts as their own.
It's easy. Even if you don't know the original source it is easy. Examples:
"I read somewhere, maybe Entertainment Weekly or maybe it was People, that..."
"I heard a great quote from [INSERT MOVIE TITLE], and it really made me think. It said..."
"Have you ever read [INSERT BOOK TITLE]? There is a great quote that really applies. It said..."
"I'm not sure where I heard this, but I heard somewhere a saying that really captures this situation..."
It is important that you know that I don't stay angry for that long, and when I say angry, I really mean I'm bothered a bit. I just think that we shouldn't take credit for something that isn't ours.
Also in the category of things that bother me: Disseminating information as if it were fact, when in reality, you have minimal or untruthworthy information about the subject.
NOTE: This is by no means definitive. I think there is kind of a code of ethics that applies to the subject. Does the information really require a citation? If so, how thorough? Is it common knowledge or common language? And so on...