I think the difference is that sellers opt in to sell through Amazon, and probably sign a contract allowing Amazon to collect and display feedback; Yelp is oper

I think the difference is that sellers opt in to sell through Amazon, and probably sign a contract allowing Amazon to collect and display feedback; Yelp is operating without the seller's explicit consent. So unless the rating site can lock in a huge swath of consumer demand and so demand that sellers consent to allowing feedback, the artcle's point about independent rating sites stands.