Tom Hespos was focussing on ad targetting in this blog post, but he’s accidentally made a powerful case for trusted references.
As much as we might not like to admit it, what we perceive our needs to be is heavily influenced by our friends’ needs. You might be perfectly happy, thinking all your needs are met, but if your five best friends suddenly purchase new cars, new Kindles, or a new style of clothing, it’s likely that you’ll consider buying these new things yourself. To paraphrase George Carlin, rest his soul, coveting other people’s stuff is what keeps the economy going.
The influence our friends have over our purchasing habits isn’t automatic. Of course, we have to know about our friends’ purchasing habits. Once we know Fred bought a new Honda Accord, we have to go through a consideration process of our own. Getting to that consideration in the mind of the consumer is the classic challenge for most marketers.