Several times in the last week or so, I've heard people talk about the shortcomings of LinkedIn. Personally I've found it tremendously useful and efficient, but Jack Yan has a good point in his post, LinkedIn needs more.
"LinkedIn does not really reﬂect the roundedness of an individual, and business connections are best formed with people with whom you have some non-business commonality.
People are almost forced to become more human in Facebook if they frequent it."
Therein lies the strength and weakness of Facebook compared with LinkedIn. Which one you prefer reflects your philosophy of doing business. Some people wish to separate business and the rest of life, others, as Jack points out, wish to do business with whole people.
While it's possible to show a bit of your humanity on your LinkedIn profile (plus a link to your blog, which I always check on people's profiles), Facebook gives you more of an integrated package.