I'm not sure that word-of-mouth marketing is the most effective tool for gathering together alumni for a high school reunion. I officially graduated high school the summer of 1998, though I had spent my senior year as an exchange student in France. I had been wondering if they were holding a reunion, but figured someone would notify me; they've found me in the past and I updated my information in their online directory.
A high school aquaintance of mine found me on Facebook and asked if I heard about the reunion coming up in two weeks. Coincidently, we'll be driving through the area the day after on our way back from a family Thanksgiving, so I'm very tempted to go. I just wish I knew who was coming so I knew if it was worth missing an evening with my family. Most of the people I hung out with either live out of the country or their family doesn't live in that area anymore.
What does this have to do with libraries? I guess Web 2.0, and word-of-mouth marketing. I'm a big fan of word-of-mouth marketing, but sometimes it's just not the best tool!