These days, integrating mobile apps with major social networks is a common practice, and for good reasons.
By interacting with social networks within your app, users are spreading your app’s name and message in those networks. Think of Facebook’s billion and Twitter’s 500M active users and you will have 1.5 billion of reasons for considering to add sharing services to your app.
As for iOS 5, iOs SDK has native support for Twitter and iOS 6 has brought Facebook framework as well; but most Social Network Portals have their own OAuth based API, that you can also include in your app.
If you are convinced now and you want to add sharing services to your apps, I encourage you to give a try to ShareKit 2.0 framework.
ShareKit is an open source framework that brings drop-in share features for all iOS apps. Its installation is very straight forward, step-by-step instructions can be found here.
Try it, and you will see that with ShareKit the real challenge is not to add sharing capabilities to your app, but to understand why you would want to and how it will benefit you and your users;)