The LinkedIn App for the iPhone is another social networking app the works only with one specific service. Just like the MySpace and Facebook apps, the LinkedIn app has been created by the company directly to offer the best integration into their social networking experience that they're willing to allow. If you're not already familiar with LinkedIn, you should definitely check it out, considering that it's been considered the adult/business version of Facebook.
The app is very straight forward and is very easy to navigate for new LinkedIn users. The main page shows you all of the new connections and updates that your connections have made over the past few weeks. From there you can view their pages directly and easily contact them. There's even a function to let you add them to your contacts in your iPhone, which is something that Facebook seems to lack.
If you've got a lot of contact on LinkedIn, this app will be very useful to you. But if you're just starting out, you'll find that you log into it very rarely. Those new to LinkedIn will notice the status update area first. While this is similar to Facebook, it has a more professional feel to it so you may want to just observe what others write in there before you brag about your big party weekend.
LinkedIn was the last of the three major social networking sites to get into the mix with an iPhone web app and now with their regular iPhone app. They've got things going fairly well for them, as they're aiming at a different audience then the other two, but that doesn't mean that this app is very handy. Usually people only log into LinkedIn when they need to contact someone, so this might be more of a last page app then anything else.