I joined Facebook. After years of thinking such things were too frivolous for me, one random thought about an old friend got me wondering who I might find if I joined.
After less than 24 hours I had reconnected with half a dozen people I hadn't heard from in years. After 48 hours that number had more than doubled. I've had a nice e-mail exchange with my high school prom date.
A few months earlier I somewhat reluctantly joined LinkedIn, the businesslike version of Facebook, and found it potentially useful, but pretty dull. Facebook is just plain FUN!
Stuff like this was unheard of in the 20th Century. I'm glad I finally made it to the 21st.