The whole point is to protect artists who are trying to make a living doing their artwork, music, writing or any other media. They don't want to be paid to do artwork for someone else such as an advertising firm, they want other people to appreciate their work and support their ability to do that artwork. They want freedom to produce art without a patronage system imposing ideals upon their work. This is the entire basis for copyright, that the artist can expect to profit from others' appreciation of their work rather than being walked upon. Without this ability to own one's own production, art by anyone except the rich would very likely cease to exist simply because the artist would not have the time to produce said art. Anyone arguing that someone merely linking to something has no complicity in breaking that agreement are taking semantics to an extreme I do not expect from intelligent human beings.
I do not expect LJ to enforce this sort of issue, rather I do support copyright and do not feel it is the fault of copyright law that these issues are not clearly defined. Anyone placing an image in a magazine is publishing it. The person buying a magazine which has violated copyright law is not responsible for the magazine placing that image there, in whatever fashion, so it does not really follow that the publisher is not responsible. They are the one who chose to place the image, not the buyer. The artist should not be forced to hide and seize their work from every accessible place for fear that it might be stolen, rather it is the responsibility of the person wishing to use a copyrighted image to contact the artist or writer, not the other way around. I never heard of any writer being required to contact a school before someone failing to quote them correctly in a paper would get in trouble for plagiarism...that is somewhat comparable to waiting for a lawyer to contact LJ before asking users to correct their behavior. Common courtesy for the creator should be enough. : /