I've been a user of Facebook for a number of years now. My usage comes from its origins in university campuses. It was my friends who are in Cambridge University who first made me aware of it and whose avid use of the site made it worthwhile. For all the time I have used it, I've used it exclusively for non-business local friends, mainly linked to the university. This has enabled me to maintain almost two online identities: a business identity suitable for the business world and a more social local identity suitable for my local friends. For the former I've used LinkedIn, for the latter, Facebook.
In recent years Facebook has spread from university campuses to the wider world and I have had more and more friend requests come from people outside Cambridge University.
As Facebook only allows you to create one account and that account has to use your real identity, it hasn't been possible for me to create a separate business account so I've continued to resist, funnelling business contacts into LinkedIn and ignoring friend requests from the business world.
Today, I've given up. I have adjusted my Facebook profile to be more suitable for the business world and will henceforth be accepting friend requests from close colleagues, non local friends and business contacts.
The trigger was two things. First, attending Le Web 2008 in Paris and seeing almost the entire audience's hands go up in response to the question "who uses Facebook at least once per day". The second was the launch of Facebook Connect which allows the real name/unique account aspect of Facebook to enable real identity authentication on other sites. A service that useful cannot be ignored.
It's a very simple one page website, powered with a very simple question answering API that sends a text question to our platform and prints out the text response returned.