Content (articles/blog posts) copied on a content aggregator is quite possibly of interest to a great many people. The original author deserves full credit and

Content (articles/blog posts) copied on a content aggregator is quite possibly of interest to a great many people. The original author deserves full credit and ownership of that content (unless they work for some company, then their employer owns the content). Content on Facebook is more likely to be conversations between friends or information about a person (their employer, music tastes etc). This information is likely to only be of immediate interest to the individual who posted it, and to their friends. So copying information from an article/blog post and passing it off as your own is like a newspaper ripping off another newspaper and doing no reporting of their own (or buying content for Reuters ;-) ). Repeating content from Facebook is like repeating something you overheard in a casual conversation between friends (unlikely to be of interest unless you know the people in question). Not sure what analogy would apply to Twitter.