Last week's Morgan Freeman death hoax is only the broadest, most recent incidence of internet trolls hoaxing an easily transfixed Twitter audience. Tuesday afternoon some bored tweeter tried a little narrow-casting, making up a Matt Holliday injury, adding some odd specifics, and posting it to an @Cardinals_ account, for people who aren't looking very closely to notice and freak out about.
↵By 4 PM CDT it had spread through the #STLCards hashtag, the end result looking a little something like this after some civic-minded hashtag citizens Snopes'd it:
↵↵↵FAKE, PEOPLE. #STLCARDS RT @cardinais_: OF Matt Holliday scratched from tonight's lineup. Injured knee on hotel steps. Possibly torn ACL.
↵— Chris Reed (@birdbrained) September 11, 2012
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↵What causes one of these hoaxes to spread isn't necessarily the initial fake tweet, which I never even saw—most people might be able to tell something weird is going on, there—but the rapid responses to it that treat it as a fact and then, say, add on the tweeter's unpleasant hope that the Cardinals and their fans are ready to watch 20 games' worth of Shane Robinson in left field.
↵Because of the churn and conversation inherent to Twitter, this kind of thing is an easy hoax to spread—luckily, it's also an easy one to tamp down.