I have a few contacts on there. Only because I was hit up by them. I see how it can be useful in the business world.
It's almost like Facebook for the business person. You use it to network with people and helps you find jobs or you can post jobs. I have not used it as such, but have a few people linked that use to work at my work. I get pinged every once in awhile from them with updates on their status.
We are trying to utilize it as a tool to make connections with other business people. But it does appear to be a great way for the headhunters to recruit.