Anecdotally, I am a passive LinkedIn user - we're out here. To me it's a glorified address book of thousands of current/past coworkers, I only ever connect with people who I've worked with professionally. All notifications (email) are disabled, I might log in once every month or two to accept connections and initiate some but that's about it. It's a tool, I treat it like one. $0.02
I imagine there are a lot of passive users of linkedIn. I found the article interesting as I have been considering deleting my account too and share similar emotions.