Facebook is a good way to inject a little personality into your business. Your website probably doesn't have a lot of insight into your personality on it, but your facebook page can.
The point of facebook is to interact with other people, not to be something boring that you update once every six months. You should have some personality on there so that people can "get to know you" a little bit. The trick is to decide for yourself how much you want to put into it.
You have to decide for yourself what tone you want to set with your online posts. Just remember that facebook is forever, just like everything else that you put up online. You can delete some things, but some you can't. So if you have a client who is driving you crazy, it's best not to put that up for all to see (including the client, most likely.)
I know of a few facebook pages and twitter accounts that are really funny, but they're rarely about the business. The owners post funny sayings, jokes, random thoughts, etc., and while they're amusing, I wouldn't be able to tell you much about their businesses.
Then there are pages that are completely business-oriented, with no interaction with the people who have said that they "like" the page. Kind of an announcement-only page. I personally find those pages really phony, and they don't interest me much.
I have a personal facebook account that I rarely use, but I keep it because I have friends and relatives on it. Real friends, not random people who I saw in a crowd at some point. The business friends that I have on there are put into a list, and the lists are managed so that if I post about something going on with my kids, not everyone in the wedding industry will have to see it.
I post on my business page a lot, and I keep it pretty casual because I can't stand it when it's too formal. There's a certain level of sarcasm that dwells within me, as anyone who knows me will know. If I tried to be completely "professional" and never inject any humor into my posts, it would come off as totally phony. So I post things that are cake-related, but I'll also comment on other non-business related topics.
You can also link your facebook account to twitter so that your facebook posts show up there. And using networked blogs, you can link your blog to facebook so that when you post on your blog, it goes to facebook too. That's another way to help people "get to know you" so to speak.
Kara Buntin owns A Cake To Remember LLC, custom wedding cakes in Richmond VA