Question: I consider Facebook to have information that is personal and that I only share with close friends and family. However, in my new workplace I’ve been asked several times for my Facebook username and/or have been *friend requested* and I don’t want to sound rude by telling them that I don't want to add them as friends. 

Any suggestions on the way I should handle this?

Answer: 
I have a blanket policy - I don't accept Facebook requests from anyone with whom I have a current business relationship through my employer. That can be vendors, co-workers, contractors, or anything else.

If someone sends me a request, I tell them politely "I'm sorry, but it's my policy to not accept friend requests on Facebook for anyone I work with." This hasn't caused me any issues yet; people understand and accept it.

Doing this saves me the trouble of:

* Worrying about Facebook changing privacy settings;
* Having to maintain a "restricted" list;
* Having to explain to people why they're on a restricted list/why they rarely see anything from me (if they figure it out);
* Dealing with the minefield of "but you added `<person X>`, why not me?";
* Accidental over-sharing, possibly at the hands of a previously-unknown mutual friend.
My policy, that has served me well, is that I never, under any circumstance, add coworkers to my Facebook "Friends List" until I have left the job.

I can't see any good coming out of adding anyone while we are still coworkers. I don't need anyone monitoring my every move and I don't like having to think too hard about who is in what group when I am sharing opinions and personal thoughts. 

What if I decide to post that I'm heading to an interview (which I do occasionally just to test the waters) or if another friend asks me about a recent interview experienc? 

Can everyone I work with be trusted with that info? Even if one person can be trusted, they are like a vector by which another (untrustworthy/gossipping) employee could gain access to information I provide. 

What happens when a nosy or hostile coworker steals a glance at their phone FB wall while they are distracted etc.

No coworkers...ever...this works for me since I tend to change jobs every 2-3 years anyhow. While I'm at a job, if we really are friends, then we probably don't communicate primarily through FB. If we are friends, we will have each others phone numbers and can text/call/im/email to arrange pretty much anything.