Sometimes, this can quickly lead to a downward spiral effect at the company. Productivity falls and whatever issues the layoff was intended to remedy end up being magnified instead. This is usually the case when - before the layoff - there was either "writing on the wall" (that typically management wouldn't admit to publicly) or an inherent distrust of management.
What really sucks is the pile on. Recruiters watch for these moments and jump on them like piranhas. They notice a sudden spike on LinkedIn of resume updates by people all working at the same company and hone in on those still there, reaching out to see if they want to take a look at other possibilities. Simply put: no one wants to be the last one to go down with the ship.
Whatever project you're building/working on, please remember those who weren't laid off, too.