Disclosure: I run an online writing instruction program called Time4Writing.com.
There's a lot more to be said about how to teach writing as the language, media, and technology advances. I first started thinking about this when I was looking to create a program to teach writing.
When we were working on the initial concept for teaching writing, I did wide-ranging research on teaching writing and what it should consist of. I studied the six trait writing methodology that is widely adopted. I read about the five paragraph essay that is generally the focus of writing tests on standardized tests such as the SAT, FCAT, and so on. I tested and met with the vendors of the AWE systems. AWE stands for automated writing evaluation and it's a super-hot trend as a technology. Key vendors: Vantage Learning and E-rater. I read a variety of books on teaching writing rating from the most pedantic textbooks to exhilarating books like: Eats, Shoots, Leaves.
At different points, I was convinced that we should do something highly innovative. I developed a variation on the six trait writing approach which focused on the reality that people write very differently whether they are writing for the web, a newsletter, a school paper, a text message, or a printed journal. I postulated that a key concept was that as you write, you should adopt yourself to the media. Without that obvious first step, "teaching writing" seemed to actually mean; "teaching writing for school ONLY." I worked closely with a few AWE vendors to explore OEM possibilities. I loved much of the new thinking including the idea that emoticons represented the start of a new form of punctuation and that text shortcuts would become acceptable in English (ideas explored in Eat Shoots Leaves).
Ultimately, Time4Writing turned out to be more responsive to perceived student needs than anything else. While Time4Learning teaches grammar and vocabulary and many other key writing skills, there remained a need for teachers to help students grind through building the skills of constructing sentences, paragraphs, and essays. And this is the current focus of Time4Writing.com.