Size is just a number. Unless you stop using a number and qualify with adjectives like large and small. Implicitly, when speaking of companies/organizations, we somehow associate young and old with small and large respectively. We associate the term start up with a young and small company. But more accurately. there's a sub-conscious association of various characteristics with such a company - agile, ad hoc, tech-savvy, dynamic and lively, top-notch folks.