For me, it’s always hard to find someone with both the system / product knowledge and the instructional design skills to match.
It is easier to be the Instructional Designer and SME. I started really as the SME building my own (Moodle) course for the various TAFE units/clusters I was teaching. Later, based on that strength, I was given the task of building other material that I knew little about. It was much more difficult, but I found I had to understand the material (to an extent) to do any course justice. A Learning Designer doesn’t need to be a Subject Matter Expert, but they need to have a vision of the subject just to have the inspiration of how to craft the path you’ll take these students down.
Perhaps your opinion differs. Comment here, or comment on Julian’s blog. Let’s get a good discussion going.