I used to think that LinkedIn requests were obnoxious. I felt like I was being roped into a social network that, unlike Friendster, has been scrubbed free of interestingness and instead has a glossy PR sheen. But as a business professional, it's become unavoidable; not having a LinkedIn profile is like not having a business card to hand out at conferences. Web Worker Daily has a bunch of reasons why you need one. Here are a few of my favorites:
Improve your Google results. When someone Googles you, do you really want the first thing they see to be your posts on the fly fishing forum? As your LinkedIn profile will have a fairly high Google PageRank, it should rank fairly high in your search results. And you can fill it with stuff you want people to see.
Easy resume. Don't feel like creating an old-fashioned resume and photocopying, faxing or emailing it to 20 different companies? Create a LinkedIn profile that serves as a resume, and then send people the URL. Be sure to get a vanity URL for this, as you can set the URL of your LinkedIn profile.