Articles from news sources like AP and Reuters are often reprinted in other publications. When you find an AP article on another site, say MSN, do you cite AP or MSN as the source of the information?
Depend on the writing context or clients' needs I may or may not cite news sources, but often when I have to quote someone's words.
That's because they paid AP/Reuters. It's called the wire budget (or budget or something else depending on the publisher). As for the citing, I'd go with the original unless the context of the cite calls for citing the "user."