I get this question all of the time... "Why do I need a LinkedIn?". Many people don't see the purpose of it, what are you going to be doing on that site anyways? Well, if it's what your thinking, you're absolutely right. There is zero purpose in having a LinkedIn if you aren't doing anything with it. However, if you're not on LinkedIn, you're missing out on a top resource that recruiters are using these days.
Here is a great article on how to get recruiters to look at your LinkedIn and give it purpose.