I think this technique is bullshit. I have a few people on LinkedIn that I don't know very well. When I find that I can a connection-of-a-connection through them, it's a big groaner. Because I know that I can't use them for a recommendation and be like: "Yeah, we shoke hands once at a tech meetup."

My current policy on LinkedIn is only link to people to whom I could give a warm referral or expect one in return.