It seem like an illustration of the power of reciprocity in social psychology.[1] You give something away for free and then those who took what you gave feel ob

It seem like an illustration of the power of reciprocity in social psychology.[1] You give something away for free and then those who took what you gave feel obligated to give something back to you. I sometimes wonder if those who give away their book for an email would get more emails if they would first give away their book and only then ask your email. [1] https://en.wikipedia.org/wiki/Reciprocity_(social_psychology)#The_power_of_reciprocity https://en.wikipedia.org/wiki/Reciprocity_(social_psychology...