I think the question is what a business is going to use Twitter or LinkedIn for. Twitter is great if your a large business and you want daily, instant consumer reaction. However, for people who follow hundreds or thousands on Twitter, a few Tweets a day from a company may not even be noticed. A good LinkedIn page, however, is almost like a company Web site, with lots of good, detailed info and links.
I compare linkedin more to facebook in that I find and am found by business people from my past that turn out to be individually valuable to my network, and also let me expand my network.
In the business world, people change jobs and careers so often that it can be easy to lose track of the individuals you worked with or had a connection with.
I’ve had several people who I had a good working relationship rise to the top of the heap making them even more important to keep up with, but I wouldn’t have know of their success or stayed in touch without this service.
Linkedin is many more times valuable and useful that facebook will ever be for me.