That's why I made the comment about disproportionate benefit. It is clear that news organizations want, or at least feel compelled, to use social media as a promotional tool under some circumstances. Yet they don't like the terms that social media sites offer them.
In some respects, I don't blame them. If most people just skim the headlines and never click through to read the article, newspapers would be better served by their readership going to their own landing page. The other option is to recognize that the title and summary have intrinsic value, in which case the news organizations should have the right to request compensation.
I realize that there are other factors to consider here. For example: end users sharing links, either as information or to solicit discussion, should be considered a form of expression. Unfortunately, the business interests of social media sites muddies the waters.
Don't you think they would have stopped if they felt they were being harmed by it?