be simply a worn out punchline in trivia quizzes, a pop culture flashpoint in the early 21st century that lasted for a few years and was gone just as fast. I think it would be worth writing a series on the Fall of Facebook.
Other title concepts:
The Great Facebook Implosion of 201x.
The Facebook Disappearing Act
Facebook Evaporation Day
Billionaire today, punch line tomorrow.
Facebook Emigration Day
Facebook Independence Day
The Rolling Facebook Evacuation Plan
People in each time zone transfer to new service at certain hours of the day to balance the load on the servers. It is estimated that Facebook could be a ghost town in 24 hours or less.
Here's an interesting teaser by Cringely. Link.