Go ahead and complain a little, because expressing yourself is protected free speech, including on social media sites.

From nytimes.com:

"Employers often seek to discourage comments that paint them in a negative light. Don’t discuss company matters publicly, a typical social media policy will say, and don’t disparage managers, co-workers or the company itself. Violations can be a firing offense.

But in a series of recent rulings and advisories, labor regulators have declared many such blanket restrictions illegal. The National Labor Relations Board says workers have a right to discuss work conditions freely and without fear of retribution, whether the discussion takes place at the office or on Facebook.

Damn straight. What do we look like, China?

In addition to ordering the reinstatement of various workers fired for their posts on social networks, the agency has pushed companies nationwide, including giants like General Motors, Target and Costco, to rewrite their social media rules."

There does seem to be a line in the sand, however.

"The labor board’s rulings, which apply to virtually all private sector employers, generally tell companies that it is illegal to adopt broad social media policies — like bans on “disrespectful” comments or posts that criticize the employer — if those policies discourage workers from exercising their right to communicate with one another with the aim of improving wages, benefits or working conditions.

But the agency has also found that it is permissible for employers to act against a lone worker ranting on the Internet."

O.K. Let's review.

Rant about your employer if you can get a bunch of other people to join in (that shouldn't be too hard).

Make sure you throw in some distinct comments about improving your work situation, but possibly avoid the "when the boss dies prematurely" line.

Then, ask yourself this question: did you remember to unfriend him or her? :-D