Of course, you might not have the luxury of separating work and non-work social circles. Your company might have a policy requiring -- or strongly encouraging -- intra-office Facebook activity. Alternatively, you might need to run certain teams, programs or client relations through Facebook. Possibly, you just have a thin-skinned supervisor who wants to friend you, or who thinks that a little Facebook interaction will raise their approachability quotient. In these cases, you're probably stuck friending your coworkers.
If so, there are advantages to establishing a separate Facebook account for business contacts. Such an account renders the process of monitoring your exchanges for appropriateness much easier -- you'll only be engaging in shoptalk anyway. Better still, no one can criticize you for posting on company time.
If you decide to go this route, you'll probably want to switch your personal Facebook to use a login and e-mail account unrelated to your name or company: If someone from work Googles your name, you'll want them to find your "official" site, not your fun site.