In LinkedIn's own words: "A Company Page is a place for companies to provide more information about their products and services, job opportunities, and company culture. Any LinkedIn member can follow a company that has set up a Company Page to get updates on key developments."
We logged into LinkedIn and checked out the company page for Google. They have over 350,000 followers, almost 40,000 employees on LinkedIn, and are advertising 1,200 jobs. Facebook has almost 120,000 followers, 4,000 employees on LinkedIn and is advertising 17 jobs all over the world. LinkedIn also lists the careers that may be interesting to you and offers a suggested list of companies you may want to follow based on your resumé.
It is fairly easy to add your company page to LinkedIn. There are some security controls in place to make sure the wrong person doesn't claim your company name. If you do choose to claim your company on LinkedIn, your best plan of action is to make sure that it has fresh content to entice followers. There's nothing worse than a company page that has no followers. You can also ask your colleagues to "recommend" your company, which again adds content to your page. One very important feature is enabling your RSS blog feed to post to your company page on LinkedIn. Since you should be updating your blog on a regular basis, this too will keep your company page full of new posts.
As with Google+ brand pages, LinkedIn's company pages might not be a necessary evil (i.e., time-suck) for now, but they may be in the future. It is worth keeping an eye on LinkedIn, as a company page may someday be as important as having your website and Facebook fan page.