The fallout of the Facebook IPO keeps getting worse. On the second day of trading, Facebook shares tripped their circuit breaker as prices dropped more than 10% in the opening minutes of trading. This is very unusual for an IPO, particularly one as highly anticipated as Facebook. Recall, these individual stock circuit breakers were implemented following the flash crash (which occurred on May 6, 2010). See the article here (Wall Street Journal).
Dolvin, Steven D., "Facebook Trips Circuit Breaker" (2012). All Chapters. 2.