For years, Facebook's top bench of executives has been a vision of stability. Not anymore.<br /><br />Instagram co-founders, Kevin Systrom and Mike Krieger abruptly resigned on Monday.<br />They are the fifth and sixth major names to leave Facebook since September last year. <br /><br />The departures comes months after a published detailed analysis on how no one leaves Facebook. <br /><br />All have quit for different reasons. <br />
