There are distinct limitations- there is a team that "polices" memegen and will send you (and your manager, and HR) threatening emails (including suggesting job termination) if you post something that's not very nice.

Back in the day somebody made a meme which had a D&D alignment chart for all the Google leaders- Vic Gundotra was Chaotic Evil, while Urs was Lawful Good. Had to take it down because an SVP complained.

And who wouldn't expect otherwise? Their lucky it just got taken down and they didn't get fired.

It boggles my mind that people think complaining about work - ON WORK TIME AND WORK RESOURCES - is some sort of protected activity. Freaking stupid.

Having an idea of how employees feel, as well as an outlet for their frustration, can be productive.