S09.5 · Retail & Commerce
Amazon-led marketplaces facing discovery disintermediation as AI shopping agents bypass sponsored search.
Amazon's gross merchandise volume reached roughly $830B in 2025, and third-party sellers now account for 69% of it, up from 60% in 2019 (Marketplace Pulse). Global e-commerce sales run an estimated $6-7T — a wide range, because marketplace, brand-direct and B2B volumes blur together depending on scope. Growth has decelerated to single- or low-double-digit from a historical pace above 20%. The economics, though, are the point: this is an internet platform wearing a retail label, and its discovery layer is the single most exposed asset in the sector to agentic AI.
Marketplace volume concentrates in the US (Amazon, Walmart), China (Alibaba, Pinduoduo) and Latin America (MercadoLibre), and seller supply is increasingly China-sourced regardless of where the buyer sits. Concentration is extreme — Amazon alone represents roughly 36% of total US e-commerce (Marketplace Pulse). Millions of third-party sellers feed the platform upstream, consumers sit downstream, and the platform collects a take rate plus advertising and fulfillment fees in between. Asset-light, take-rate-plus-ads is why marketplace economics trade on internet-platform logic rather than traditional retail logic.
The shift from Amazon selling first-party inventory to hosting third-party sellers — 69% of GMV now versus 60% six years ago — is the structural fact that matters. It converts Amazon from a retailer bearing inventory and merchandising risk into an infrastructure layer collecting rent on other people's inventory. Sellers pay for placement, fulfillment and increasingly advertising simply to be found inside a search result they do not control — the exact mechanism now under threat from AI agents that search without ever scrolling a results page.
Fulfillment build-out holds seller lock-in and delivery speed; advertising is where the new dollars land, and it has become the primary profit pool. The core threat from AI is discovery disintermediation. An AI shopping agent that compares and purchases across sites on the buyer's behalf collapses the "start your search here" moat two decades in the building — and with it the sponsored-search revenue that funds platform profitability, because sponsored placement only earns when a human is scrolling a results page.
Inside the segment, a boundary is forming between platforms that control the agentic-checkout layer itself and those reduced to being an inventory feed for someone else's agent to query. The first group keeps the customer relationship and the margin that comes with it; the second becomes a commoditized supply source. The shift is already underway, with structural impact expected within 2-5 years.