That reminds me of the first time I caught a plagiarist at a newspaper, where I was a college intern.
The guy had been writing business book reviews for many years. He was a freelancer, and his work was extremely erratic -- one week, he'd be pushing the editor because his piece was cut for space and delayed a day, the next three weeks he'd have nothing and blow deadline after deadline.
Something bugged me about his phrasing in one piece -- it seemed far too clever for his typo-ridden dreck. I Googled it, and lo and behold, he'd been getting away with tacking his own bad leads on other people's book reviews (typo-ridden transitions added and altered) for years.
He was out very shortly. The fortunate side effect was a boost to my reputation as a young editor.