Let’s try a little (thought) experiment in verbal short-term memory. First, find a friend. Then, find a reasonably complex sentence about 45 words long …Now call your friend up on the phone, and have a discussion about the topic of the article. In the course of this conversation, slip in a verbatim performance of the selected sentence. Then ask your friend to write an essay on the topic of the discussion. … How likely is it that the selected sentence will find its way, word for word, into your friend’s essay?

In case you haven’t guessed, the question is rhetorical and the article (from LanguageLog, a great blog) is referring to Maureen Dowd’s plagiarism.  It is a fallacy though to focus only on the probability of the scenario you are trying to reject.  What matters is the relative probability of that scenario with the alternative scenario, namely that Maureen Dowd would bother (intentionally) lifting word for word a paragraph which is not particularly insightful or cleverly written from a popular blog at the risk of being called a plagiarizer.

When something happens that has two very unlikely explanations, picking one of those explanations is mostly driven by your priors.