Danny Brown has an excellent article on how everyone could do a better job measuring influence marketing.
The important thing to remember is that even after identifying and reaching out to influencers, we still have to track it with our normal processes. The sales cycle still has to be enforced. Tracking lead generation, tracking where they are coming from, pushing it all into CRM, and nurturing…and then doing the calculations to see how effectiveness of the channel.
I had a coworker years ago who went to work for BzzAgent. Find key influencers, get them to pitch products in-person (in a nice non-creepy way). They thought the same thing as Danny, influence is at a dyadic level, not just a matter of splattering ads all over Facebook.
Similarly, take a look at the NY Times article on how the Obama campaign found who to target. Ignore the politics, but it was basically dyadic relationships too. “We asked to see [Facebook] photos but really we were looking for who were tagged in photos with you”. That is how they identified voters, attributes, and how to target them”.
Eventually, none of this is cheaper or that different from any other channel.
BTW, checkout a preview of Danny Brown’s book: Influence Marketing: How to Create, Manage, and Measure Brand Influencers in Social Media Marketing