There's this member on one of the forums that I go to, who just keeps pasting full-length articles on the forum. About 95% of his 200 posts are copied articles from popular news sites like the New York Times, Yahoo, MSN, etc. I feel he's overdoing it, and it's starting to bother me. I guess the admin of the forum doesn't mind because he likes the new topics (which sometimes encourages the development of lengthy discussions).

What I'd like to know is if this is against any copyright rules, and if it is who might have to pay for the consequences: the admin or the member?

If you are in the United States i believe you are protected as long as the admin removes the content when asked to.
But in the UK.. you might get into trouble

If he gives credit, it should be okay, but it's definatley not illegal. If he were to claim the articles as his own work then that would be, I'd say he's a bit of a fool though...