a little excessive (in favor of the plagia? um, quoter) anyway

Usually this doesn't end up being someone quoting 10% of someone else's work in their own work, rather, it's a person photocopying someone else's work for whatever reason. For example, it could be a student photocopying a chapter of a book from the library, instead of buying the whole book, or a professor handing out a photocopied portion of a textbook that it isn't worthwhile for the students to buy, that sort of thing. Or the photocopying of a journal article out of a journal to which you do not subscribe, but would like to have the article on hand to refer to (and usually the library wants journals back in a rather short time).