Facebook and LinkedIn are different matters. The question to ask yourself is simple: Is this where your customers and prospects are? If so, you should be there too. Learn enough about using them to provide your message (what you do, and why customers stay and prospects should consider you), provide customers an opportunity to say nice things about you, and make it easy for prospects to find you.
If your customers and prospects aren't likely to use Facebook or LinkedIn to find you and connect with you, don't waste your time.
One other bit about the subject, since you raised it: As you think about this subject, include sites like Bizrate, ResellerRatings, and (if you're in the travel business) TripAdvisor in your thinking. Customers have plenty of opportunities to talk about you in public these days. You should make sure you know what they're saying.
And take it seriously. If someone simply misunderstood a policy in a post, clarify it for everyone to read. If they have a legitimate complaint (in their eyes, even if not in yours) and have made it public, now a lot of people know about it. Figure out if you need to do something differently.
Like it or not, if you're in business, you're probably out there on the Web somewhere or other, even if you didn't put yourself out there.
Your choice is how to handle it.
This story, "To blog or not to blog: A small-business perspective," was originally published at InfoWorld.com.