Show Me The Money

Nearly every article and blog I’ve read recently is about the significance of social media to Public Relations. I know it is important, but how can I prove it works? Whether or not social media can be measured in terms of ROI is debatable. While doing some research on different ways to measure social media, I came across an interesting presentation by Oliver Blanchard that supports the relationship between ROI and social media in this entertaining yet informative slideshow:

What do you think? Is ROI the best term for measuring impact of social media, or should something else be used?