Lawrence Lessig says plagiarism and copyright infringement are different concepts. Here's an example: 19-year-old Kaavya Viswanathan, who has been accused of plagiarism in her debut novel, has acknowledged that she did borrow language from two books by Megan F. McCafferty.
"If I use a sentence from another work and pass it off as my own without citing it or quoting it, that might not be copyright infringement because I wouldn't necessarily need permission to use it," Lessig said. "But since I'm asserting that I am, in fact, the author of that sentence, that would be plagiarism." (Harvard Crimson)
One such instance cited by the Times is the passage when the heroine in Viswanathan's book bumps into her love interest. It goes like this: 'Though I had been to school with him for the last three years, Sean Whalen and I had never acknowledged each other's existence before. I froze, unsure of (a) what he was talking about and (b) what I was supposed to do about it. I stared at him.'
In her book 'Sloppy Waters' in which the heroine unexpectedly comes across her love interest, McCafferty wrote: 'Though I used to see him sometimes at Hope's house, Marcus and I had never, ever acknowledged each other's existence before. So I froze, not knowing whether I should (a) laugh (b) say something (c) ignore him and keep on walking.'
29 cases of such 'internalization' as the author refers to her 'unconscious act' does not sound too plausible.