speedwagoning

Spreading gossip, rumors, or unconfirmed reports that rely on a chain of other unattributed sources, usually within a tightly-knit circle, and repeated often enough as to be taken as fact.

Basically, an anonymous circlejerk of damaging insinuations, that spreads like wildfire or a contagious disease, and is as catchy and easy to digest as an '80s earworm.

News reporter: Heard it from a friend who, heard it from a friend who, heard it from another you've been messing around.

Interview subject: That sounds like speedwagoning, and I'm not going to comment.