From the NAW Blog:
Personalization is table stakes for any successful e-commerce website that offers more than a handful of products. As the diversity of products grows and each item becomes more targeted in use, it’s not practical to present one’s full selection to all customers (i.e., “Results 1-25 of 151,432 products”). It falls to site merchandisers to refine those results and decide which products to present to each customer.