CIOReview on Simplifying Virtualization with Hyperconverged Infrastructure
Sadly, no mention of Scale in this article, but CIOReview has a brief discussion on convergence and the move to hyperconvergence in their latest article on Simplifying Virtualization. They talk a little about the goals and how it is sometimes believed to have been derived from converged infrastructure.
A very high level overview, to be sure, and not very technical and might decide to do some defining of their own. But I think that it helps to give a good overview of the space.