When people speak of social networks, a lot of the conversation these days is focused on Facebook and Twitter, but in the business world, LinkedIn is where the action is. Today, the business social networking site has started offering a "Share" button to web publishers, very similar to the one already available from Facebook. The new button allows readers to share content from sites they visit with their LinkedIn connections. Several button sizes and options are available for publishers to choose from. Competition in the sharing area is of course very high, with many sites already offering Facebook, Digg, and Twitter buttons. It's unclear if many sites will jump in and add LinkedIn sharing links, or if those will remain confined to the business world.