> In short, an "anonymous source" isn't just a reporter making something up.
Is there really any difference who made it up if at the end the story came out false? If you look well enough, it's not hard to find people willing to say what you want to hear, and lying by proxy is not much better than lying outright.
> It's also rare for these sources to lie. These sources are real people, after all.
Implying real people do not lie? They do, all the time. Even more often, they are misinformed, mistaken, confuse their wishes for real fact, exaggerate their knowledge, etc.
> I can point to any number of anonymously-sourced stories that were later proven right by official announcements.
I can also point to any number that were proven false. E.g. CNN reporting Comey expected to refute Trumps words about not investigating him, and Comey confirming Trumps words. Or the same Comey calling NYT reporting "almost completely wrong" (I guess they got Trump's name correctly?) Not to mention that hilarious Fusion GPS "dossier". There's a ton of this stuff around, all the time. It's a free market - if there's demand, there's supply, and man, is there the demand.
> There may be some that can't (yet) be judged, such as the persistence rumours that X or Y may resign
That's a nice one because eventually everybody resigns (or gets fired, but that is usually also framed as "resigned", see Spicer), or dies. Since the former case is much more frequent, one can always bet on the rumor that X or Y may resign - eventually it will become true. It's just not true yet...