Here's something else that should make you think twice about online venting. Even in a "closed" Facebook group, your comment can be part of a screen shot emailed by another group member to your boss. So what's thought to be "private" has become the opposite. Good luck keeping your job after that gets out.
The bottom line becomes this: If it's something you wouldn't say while sober and in person, don't say it online. And be careful with whom you connect and friend. Social media has become part of the fabric of today's society. Embrace it, but do so wisely and make it work for you, not against you. Good luck!