Thanks Jeff for adding thoughts, and Tom for starting this off.

I think the concept of the "Implementer" is fantastic, and vastly under-appreciated, though I refer to it as the "architect". To me, that difference, while minor, suggests that this person has not only the skills to see the ultimate goals and corresponding plans of the project, but also the responsibility to assume ownership of the long-term viability of the site (much like a "capital A" Architect).