My take in this that while employers should respect the privacy of their employees, they have a reputation to maintain for their business. I think that maybe it is better off that during work hours there should be limit on Facebook activities at work and that employers should not have access to their employees social networking stuff and try to use it to discriminate them in the work place. Anyone that tries to monitor the information should take responsibility to maintain the anonymity of the person or people involved in the incident. Now you work at sensitive organizations say like top-secret government branch for example, I think you as the individual should realize that certain rights do not apply and that you surrender ALL privacy in the name of national security. However, this is an extreme case.

A good compromise is that if you maintain a responsible composure in the workplace, you must also practice the same responsible composure outside the workplace. That said, with the distribution of the internet at the speed of light, you never know what personal and private information can emerge, and the consequences could be regrettable and problematic. When in doubt, post little information of yourself and activities and try to keep a low mild manner profile. This ensures the professionalism in the workplace.