Digital Tying, Platform Envelopment, and the Tyranny of One-Stop Shops

Digital ecosystems increasingly expand through platform envelopment, leveraging their user base in market A to enter market B through tying or pure bundling. Drawing on a systematic analysis of the economic literature and EU case record, this article brings dispersed insights into a single analytical framework. We show that brick-and-mortar and digital markets are not simply variants of the same setting: network effects (or data-enabled learning), economies of scope, and interface-driven behavioural frictions alter both the plausibility of efficiencies and the magnitude of potential foreclosure. We also consider that the convenience narrative inherited from brick-and-mortar one-stop shops is unreliable in digital markets, especially when the dominant firm controls the user interface and exercises governance over consumer choice. Building on this, we propose a rebuttable presumption of foreclosure capability when three cumulative conditions are met: a qualified gateway advantage in A (nonreplicable distribution or on-platform integration); amplification in B through network effects/data-enabled learning plus behavioural frictions; and low incremental investment at the distribution level. The proposed methodology is not a per se rule against integration, but a balanced approach that combines efficiencies with democratic choice and is intended as a practical step towards the definition of ecosystem theories of harm.