After watching ST:TMP for the first time in 25-or-so years, there was an interesting familiarity to the behavior of V'ger as it approached Earth... Kirk, Spock and Decker discovered that the Voyager probe had contacted a world of machines in a distant corner of the galaxy (the Delta Quadrant?) which upgraded it to accomplish its mission of gathering all knowledge and return that knowledge to its creator.
That takes us to ST: First Contact. After Picard foiled the Borg attempt to assimilate Earth on "First Contact Day", they transmitted a set of message to the Borg (the "upgraded" V'ger) of the past. A century and a half later, V'ger comes trundling in like a juggernaut, assimilating everything in its path - not destroying, but converting it into energy as information. V'ger creates the first Locutus from Lt. Ilea and learns that machines function best in union with carbon-based units. And with all the proper FOF codes directly inputted, V'ger bonded with Decker and quantum-transported back to the Delta Quad.
Thus, with renewed purpose - a far more pragmatic purpose than general information collection and storage - V'ger instructed its mechanical patrons on the new assimilation protocols because carbon-based units are more effective in union with machines, just as machines are better in union with carbon units. And this is how the Borg came to be.
Or is it? Feel free to support and debate the theory.