Today they are smashed together out of habit, because that is what we are used to in the physical world. We browse the products on the shelves, ask a sales clerk for advice, pick a product, pay for it, and take delivery all from the same store. In the physical world, it is very cumbersome to segregate these activities to different companies, as the customer would have to shuttle across town for each step in the buying chain. The retail store is orchestrated around maximizing efficiencies of the physical supply chain-the logistical relationships that move the goods from production to the consumer. The consumer is only engaged in the final step with the binary option to buy or not to buy from a fixed set of options at fixed prices.
Power rests with the store.
Geographic constraints defined this optimal retail chain, one that has undergone little change for hundreds of years. Vertical integration is not optimal for consumers. Let's say you want to decide which DVD player to buy. Any one merchant knows only what you have done on that particular site. So for both objectivity and pan-Web personalization, there will be separate consumer companies that focus exclusively on product selection and reviews.