If you are in college ministry you are aware of Facebook's importance but chances are you do not have much of an interest or knowledge of LinkedIn.
Adding graduating seniors as connections on LinkedIn provides an additional layer beyond Facebook to stay passively connected. If you are in a large ministry it's a great way to meet and connect with others in a more professional manner. I've benefited significantly from making connections with other staff outside of my region, but similar in career interests.
@chrisbrogan a lot of people i know don't know how to determine someone's worth on linkedin--what makes someone valuable & worth following?
@brianbarela - I'd say the people one might choose to follow on LinkedIn would be business prospects, colleagues, or networking hubs.
Chris Brogan has written a great series of posts to help you understand it better:
Are you on LinkedIn? If you are not what is the biggest friction point in joining?