Frenemy: Someone who is both friend and enemy, a relationship that is both mutually beneficial or dependent while being competitive, fraught with risk and mistrust.

—Urban Dictionary

That’s not a bad first stab at a definition, but let’s expand on it: A frenemy can be a friend who evolves into an enemy. Or an enemy who morphs into a friend. Or a friend who seems to be an enemy, or an enemy who seems to be a friend. Or someone who teeters precariously between friendship and enemyhood, sometimes over the course of decades. One thing, however, is undeniable about frenemies: The technology world has always been rife with them. Consider these twelve outstanding examples–past, present, and future.