I just attended a reunion that was highly publicized on social media. We had almost 100 grads attend plus other guests. It was a great time. We got daily feedback from the organizers on who paid and was attending. The menu was decided online. Lots of ideas were flying around in the early stages. Plus we had a dedicated class page for all the subsequent pictures. In our case social media helped make the event a success.
http://news.yahoo.com/facebook-killed-high-school-reunion-160107228.html
A month before the reunion was to occur, I received a note that I knew was coming. The whole thing was cancelled. Evidently, only a handful of folks had actually forked out money to help pay for the food and venue rental. Everyone else was satisfied with just keeping up via Facebook.
http://news.yahoo.com/facebook-killed-high-school-reunion-160107228.html