If you work for a company and want to participate in social networking sites like Facebook, for your sake and for your employer’s you should establish a non-work email account and use that as your main link to Facebook.
You also should designate your geographic network as your primary Facebook network, and make your employer network secondary.
I use Gmail (it’s free) for my personal email, and now there’s a great application called Fmail that ties Gmail and Facebook together. It lets you do just about everything you can do on the Gmail site, but without leaving Facebook.
Is this a breakthrough convenience? Not really. I have Gmail in my toolbar favorites, so it’s not that big a deal to access it within Facebook.
But it is a good application, and it’s a sign of how open APIs that let web sites talk to each other can lead to some useful mashups.