Well, not really dark: This is in reference to Shel Isreal's recent bit about LinkedIn. Shel notes that LinkedIn is actually good for recruiting. He cites some examples of folks who assembled a team using LinkedIn to locate candidates.
Think about the other side: You're the CEO of a company. You've discovered LinkedIn. It's kind of cool. You introduce some of your team to it. Before long everyone is on LinkedIn.
I remember a recuriter friend cautioning me that we shouldn't have people supply both their first and last names in the their voice mail greetings in our brand new startup. It would make it too easy for the best people to be poached by other recruiters just dialing through the directory.
LinkedIn is an order of magnitude worse/better/more.