Its stock (ZNGA) dropped over 13% and trading has been halted.
Since Zynga’s gaming business relies heavily on Facebook as a distribution platform, those who are reacting to Facebook’s jump out of the gate could have something to do with the drop. This could also simply be a wave of tech investors dropping one company and moving their money over to Facebook.
In regards to the trade halting, it’s more than likely due to a “circuit breaker” mechanism that’s in place to stop the free-fall of a stock, adopted after the crash in May 2010.
UPDATE: Zynga trading resumed at 12:29PM ET at $7.80, but quickly halted again.
UPDATE 2: Zynga has started trading again and sits at $7.49 as of 1:42PM ET.