Amazon is already a huge part of many people's lives. Rather than dominate in market share, Amazon dominates "in reaching into customers' lives," Gartner retail analyst Robert Hetu said. Convenience can come in the form of Dash buttons, which put reorders of baby wipes or coffee beans a finger-press away.

Voice-shopping capabilities in Alexa-enabled Echo speakers make it possible to shop while doing household chores. Amazon also offers discounts for shoppers who sign up for regular delivery of frequently purchased items. Free shipping with a Prime membership makes it tempting to check Amazon first, even if rivals also offer free shipping for larger orders. And of course, Amazon offers bonuses and cash back when using its gift cards and credit cards.

The ease of Amazon deliveries may evoke goodwill among consumers, but it has hastened the decline of several brick-and-mortar retailers - in particular, bookstore chains. Amazon's size also gives it tremendous buying power. Just like Walmart and other big companies, Amazon can use that power to wring low prices from suppliers of products and services that Amazon sells. While Amazon can pass those savings onto customers, analysts say smaller suppliers might have to reduce quality or staff to cut costs. Some might even go out of business.