First, I'm very happy to see this long overdue topic on Sitepoint. All due respects to the *Tubes in cyberspace, writing is a huge part of the web.
At ther risk of sounding pushy, I'm suggesting a 'name' change for the topic. Copywriting is a very specific subtopic of writing for the web. Articles, how-to's, technical content are all "writing".
I have seen lots of 'discussions' go off track over "copywriting" vs. "web content" being used interchangeably.