I agree with many of the responses here. Facebook has very quickly become one THE ways to promote your business and to network.
Of course, you have your personal profile but then you set up a separate FAN page for your business where you post information about your business any updates or events on that page will go out to the fans of your business page. Those fans don't necessarily have to also be "friend" of your personal page.
You can also create ad campaigns and post your Blog RSS feed. It's simply another way to get your name and brand out there for people to find and see. Since much of how Facebook operates is Viral, then you have a huge potential audience who can see what you do and who you are. I had an old college friend contact me about my service for himself and for a friend through Facebook.
I recently set up my Business fan page and released it this week. You can take a look at it
HERE to see what I've added to my page. It's still a work in progress.
Also, if you want to see more about how Facebook can be used for Business check out Mari Smith's website/blog at
http://whyfacebook.com. She has a great post that list 10 reason for using Facebook for business.
Join the VA Forums group that Maria set up while you're there too!