Even the National Labor Relations Board agrees.
Case in point, two people (Moore and Callaghan) who worked at a teen center during the 2011-2012 school year were sent re-hire letters for the 2012-2013 school year. After the school sent out the re-hire letters, it learned of a Shakespearean Facebook exchange between Moore and Callahan which included the following:
"I don't want to ask permission . . ."; "Let's do some cool shit, and let them figure out the money"; "field trips all the time to wherever the fuck we want!"; "play music loud"; "teach the kids how to graffiti up the walls . . ."; "we'll take advantage"; "I AINT GOBE NEVER BE THERE"; "they start loosn kids i aint helpn"; "Let's fuck it up".
I guess that was more Tolstoy.
An Administrative Law Judge originally upheld the terminations. (More on that here). On appeal, the Board's General Counsel argued that "the Facebook posts could not reasonably be understood as seriously proposing insubordinate conduct." The Board -- I picture them smiling and nodding politely -- disagreed:
Callaghan and Moore's lengthy exchange repeatedly described a wide variety of planned insubordination in specific detail....We find the pervasive advocacy of insubordination in the Facebook posts, comprised of numerous detailed descriptions of specific insubordinate acts, constituted conduct objectively so egregious as to lose the Act's protection [Editor's note: More on that here] and render Callaghan and Moore unfit for further service.
So, yes, there are limits to what employees can say on Facebook. When Facebook discussion of working conditions devolve into straight-up insubordination, employees can be disciplined.