A speech delivered by Barack Obama in Ghana last month was the President's "most tweeted, Facebooked, and SMS'd event to date," according to Second Life Examiner (GP: although it's unclear how the site arrived at that conclusion).
The event was streamed live into both Second Life and Metaplace. The Click Heard Round the World offers its take on the event:
After President Obama's speech, there was a virtual debrief with three African experts: Ghanian musician DNA (Derrick Ashong), Ambassador Kenton Keith and African studies Professor Timothy Burke of Swarthmore College. People in Second Life and Metaplace could ask the speakers questions as well as engage in back channel chat.