For some reason, this blog post opts to call it "premature scalaculation" (novelty factor?), but the point is the same:
In the early stages of a startup, whether you're venture-backed or not, the primary constraint you are dealing with is limited resources (time and/or money). These resources should be spent trying to figure out what is going to work and not on intricate software designs, code optimization and infrastructure upgrades. Should the company indeed succeed beyond your wildest dreams, that's a high quality problem and more resources will likely become available as a result.
In startups, the technical founder often wears his skills as an architect of scalable systems as a badge of honor.
However, there is a fine line between premature optimisation and forward thinking. What you should get with a cofounder who's experienced in scaling systems is someone who will architect the system so that when it is time to scale, it won't be too hard to do so. That doesn't necessarily take much extra work - it just takes experience and the foresight that comes with it.