Thorough piece Lachlan. Enjoyed it. Good to see the "3V's Gartner identified and first published about 12 years ago are finally understood and have been broadly adopted by the industry. For proper attribution, here is the piece I wrote in 2001 first suggesting and defining these three dimensions: http://blogs.gartner.com/doug-laney/deja-vvvue-others-claiming-gartners-volume-velocity-variety-construct-for-big-data/.
Since then, Gartner has identified 12 dimensions of data management challenge and published an updated definition of Big Data that reflects (as you also suggest) the value side of Big Data equation: "Big Data are high-volume, -velocity, and/or variety information assets that require innovative forms of processing for enhanced decision support, business insights, and process optimization."
Gartner has also developed methods for quantifying the economic value of Big Data sources that companies can use to gauge investments and opportunities in information management/analytics/infosec/etc, and a data magnitude index (DMI) that can help in planning and anticipating needs for new infrastructure & architectures.
--Doug Laney, VP Research, Gartner, @doug_laney