[HelloNurse]

Recommendations are also skewed by the needs and interests of the pool of friends a customer has. I'd recommend (and brag about) a good computer keyboard or monitor to almost anybody I know, because 90% of my acquaintances spend a lot of time in front of a computer; I can make an educated guess about the small minorities who might be interested in a certain restaurant (location-constrained) or a board game or a bootleg CD; but I don't think I could "promote" to anybody things like old roleplaying games (I'm the most eager collector I know) or a graphic tablet (the handful interested people I know already have a good one).

And what about the buying potential of one's friends? Consider plants: students could help sell their student friends something inexpensive that fits in a small vase in a small dorm room, farmers could help sell other farmers enormous amounts of product.