My understanding is that employees do have the legal right to discuss certain topics without employer retribution, working conditions being one of them.
Here's an excerpt from a New York Times story on the recent "Facebook case" pursued by the National Labor Review Board:
The labor relations board announced last week that it had filed a complaint against an ambulance service, American Medical Response of Connecticut, that fired an emergency medical technician, accusing her, among other things, of violating a policy that bars employees from depicting the company "in any way" on Facebook or other social media sites in which they post pictures of themselves.
Lafe Solomon, the board's acting general counsel, said, "This is a fairly straightforward case under the National Labor Relations Act- whether it takes place on Facebook or at the water cooler, it was employees talking jointly about working conditions, in this case about their supervisor, and they have a right to do that."
That act gives workers a federally protected right to form unions, and it prohibits employers from punishing workers-whether union or nonunion-for discussing working conditions or unionization. The labor board said the company's Facebook rule was "overly broad" and improperly limited employees' rights to discuss working conditions among themselves.
Moreover, the board faulted another company policy, one prohibiting employees from making "disparaging" or "discriminatory" "comments when discussing the company or the employee's superiors" and "co-workers."
Now, this case has been settled out of court and as a part of the settlement the employer involved had to revise its broad social media policy. However, I'm sure the NLRB and other groups will eventually pursue other social media cases.
I agree that it's smart to be cautious online. However, the notion that employers can control so much of our non-working time and activity is a little too Orwellian for me. I will be glad to see the eventual establishment of legal signposts clarifying rights for both employers and employees with regard to speech via social media.