The sheer popularity of Markdown implies that there are some use cases for it. For example, Reddit uses Markdown exclusively, and I don't believe ALL their user

The sheer popularity of Markdown implies that there are some use cases for it. For example, Reddit uses Markdown exclusively, and I don't believe ALL their users are highly tech-savvy. Personally, I don't trust or use (if I can avoid it) any on-the-web WYSIWYG text editor, because a) they tend to be slow and clunky and b) it's difficult to predict what HTML they will turn out a lot of the time, and I will often end up needing to edit that HTML. Also, for common blogging / commenting tasks, Markdown is as fast or faster to use than WYSIWYG editors. I've been faffing around with a forum that won't let me use Markdown recently, and forces me to use its clunky WYSIWYG editor to add lists into my posts. It didn't take long for me to start yearning for the simplicity of linebreak - asterisk - item rather than a multiple-click WYSIWYG process.