Impact factor is what some academic institutions use measure whether their research is useful. Impact factor uses algorithms to determine how often something is cited. Being quoted (for good or ill) is the equivalent of having an impact.
Then there is actually having an impact on real life. Academics seem to prefer the approval of others in the great and spacious building to having an impact on real life. You can read more about this here. (Yes, there is an academic scandal involved, but the larger issue is whether having an impact within the walls of the ivory tower or one outside is more useful.)
