At one time Linked In was seen as a professional social media channel and an online networking opportunity.
For fun there was Facebook. But for me it is no more a source of business than the networking clubs or breakfast meetings have been. Just think about it for a moment. Networking events are generally gathering together a group of disconnected people who just like you provide services. So a marketing networking event brings together designers, copywriters, PR people, web designers, videographers and all your local competitors.
Who on the other hand gives recommendations of your skills and expertise? Your clients ... and they aren't there. So is Linked In better? It kind of started life more as a showcase for your CV, great if you wanted job offers, but not that relevant if you wanted to impress clients. Personally I have adopted the approach of only adding contacts I actually know and although some are clients, most are work colleagues in some way or other.
Some people however are actively targeting specific member profiles in the anticipation of getting business leads from what is in effect part of their target audience. What hey are doing is building a database of prospects which might amount to several thousand contacts. The trouble is because of the way they have been acquired they don't know them any more than the names on a bought in list.