Technological change enables new kinds of social interrelationship and interaction. It's by far the most powerful generator of social change. A TechnologicalChangeVector is generally a small but generic chunk of functionality - think about a URI, a brushless alternator, or for that matter a lever or a wheel - that opens up a new realm of social and technological change.

TCV is therefore both a vector in the sense of a direction, and a vector in the sense of a contagion. TestInfected is one of the more recent examples of such a thing.