520 employees is a lot of people out of work, but I have to think they saw it coming. My advice to people in similar positions all throughout tech is this: there are three signs that indicate an impending downsizing.
* Depressed Stock Value over long periods of time
* An Acceleration of secrecy and fiefdom claiming within the culture
* You look around and no one wants to come to work anymore
If you find yourself in this situation, leave. Find another job. Being caught in a downsizing sucks, but if you pay attention you can avoid them. It's important to make friends and to be able to tell the temperature of your local environment to avoid such devastation.
Edit: This can best be summarized as the well known phenomenon: "There's no such thing as a Free Lunch".