Frank Sommers explains why scaling is not only about architecture. Using ebay as a case study he says
The most amazing aspect of this evolution to me is not necessarily the technical brilliance of the solutions at each architecture stage, but the fact that eBay was able to meet the challenges of its growth with subsequent refinements to its system, all the while keeping the site operational.
Usually architecture is credited or blamed for scalability or lack of it. A lot of projects try to do a heads up on future scalability which usually delays the project. On the other hand the other extreme can be where we do not consider scalability and code for today. Frank tries to find the balance which requires not only architecture, but organizational capability.