I agree with Cory Doctorow’s idea regarding teaching writing, but I also think he missed an important part of writing. I remember a time I had with a middle school history teacher, who having graded a test in which I had to write responses he asked me how much I read. Of course I told him a lot, to which he responded “I can tell by your writing.”
A part of becoming a good writer is reading good writing and that is not for what passes for writing on most of the Internet. You certainly don’t find good writing on social networks. Reading is implied in Doctorow’s examples of writers workshops, but it should be obvious that reading is fundamental to writing. Much of how we learn is by mimicking others, so we cannot write well if we never see or read good writing.