Typically when a company announces layoffs its stock goes up. More mature companies have sometimes slashed headcount on the way to a better market situation. But when younger companies announce layoffs, the markets stop assuming they have lots of growth ahead and adjust expectations accordingly -- usually resulting in a significant drop in stock price.
Remember, back in July, Twitter announced earnings beating market estimates. This was at 4pm, its stock surged 4%. About half an hour later, CFO Anthony Noto said Twitter would not see "sustained, meaningful" user growth for a "considerable period of time." TWTR promptly plunged 10%.
http://www.cnbc.com/2015/07/28/twitter-earnings-7-cents-per-...