I had no idea that Facebook was planning on answering that question today via their link-up with the CNN.com coverage of the inauguration.
The CNN feed wasn't perfect-- it dropped out a lot-- but the Facebook integration worked really nicely and allowed for real time conversation of the sort that went on via Twitter during the debates. (David Burn of AdPulp articulates some of the reasons here.)
But what was probably the most crucial thing here is that many social media newcomers got to see what a shared experience felt like. Regardless of platform. And while clearly the inauguration was far more significant, in our little corner of the world, this felt pretty significant too.