Good point. I'd also add something from George Orwell's Politics and the English Language: http://www.mtholyoke.edu/acad/intrel/orwell46.htm , where he has a bunch of rules like the ones in this thread: "(vi) Break any of these rules sooner than say anything outright barbarous."

Rules aren't really rules—they're principles. Part of knowing how to write is knowing when and how to bend or break those principles.