Imagine that you’re walking down the street, glancing in store windows, when a store owner suddenly comes up to you and starts telling you how great their new line of summer clothing is. Now imagine a different scenario where you’re walking down the street and you run into a fashionable friend who tells you that they really like the new summer clothes at a certain store. Who is going to be more likely to convince you to check out the clothing line for yourself?

This, in essence,...