Why don't Facebook likes translate into dental patients? Because a like is the weakest exchange there is. Yes, it's reciprocity of a sort. You like mine, I like yours, and around it goes. But the data is brutal. You can pile up hundreds of thousands of likes and walk away with nothing tangible offline, a little goodwill and that's it. The reason is value. The lower the value of the exchange, the faster the sense of obligation fades, and on Facebook that obligation evaporates in seconds. There's no real debt created, so there's no real action that follows. Retailers figured this [...]