Where did the "you can use 20 seconds of anything for a week" fair use rule come from? Is it legit for anyone in any context?

From Onion:
http://www.avclub.com/content/interview/joel_mchale

AVC: What do you mean, trying to stop you? Does she send you angry letters?

JM: "Stop using our clips" and stuff. But it's fair use for a week, according to news rules. You can use 20 seconds of anything the week it airs.

i would take a bullet for joel mchale

i would take many things from joel mchale

I mean are joel mchale and talk soup dudes the only people who benefit from this "20 second rule"?
Because it seems like if you put something up on youtube, they can take it down pretty quick.

http://fairuse.stanford.edu/Copyright_and_Fair_Use_Overview/chapter9/9-d.html

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