When you trust a source on Twitter and that person trusts somebody else, does it mean you trust them, too? Add speed to this logic and what you will get is a whirlpool of information that you think is true.
If the desire to be the first to retweet is bigger than the desire to be right, you might be only spreading gossip. Just because it is public and shared by others, it doesn’t make it trustworthy, reliable and correct.