The richest man in the world, Jeff Bezos, has even more reason to celebrate. Amazon’s 48-hour Prime Day event this year just provided a glimpse of what ecommerce — and most likely, all commerce — might look like in the years to come.

Almost half of online shoppers in the US now begin their product searches on Amazon, compared with 35 percent who turn first to Google. Bezos is also pushing to broaden Amazon’s influence in brick-and-mortar operations,...