if your employer owns a device, and allows you to use it, you are not to ever use it for personal reasons, nor should you ever expect even the slightest amount of privacy for communications using the device. Even (and probably especially) if they give you permission for personal use. That goes for cell phones, pagers, computers, slide rules, everything. That means you do not log into personal Facebook, Google, or Hotmail at work. You do not use the company phone to call home. If you do any of these, you've 1) probably violated the terms of your employment and 2) have given the company/government permission to peer into all personal communications made with your employer's equipment.
You have explicit rights (in most cases) to privacy and use of the property that you actually own. That's it, the line is drawn there. I can't believe there is any controversy over this.
After reading this, I'm damn glad that i'm living and employed in Finland and not in USA.