Why Cross-Merchant Data Is Retail Media's Real Moat

Every retail media network says its data is special. Most of them mean: we have a lot of it, from our own customers, inside our own walls. That’s a defensible position — until you realise the walls are also the limitation.

PayPal Ads is making a structurally different argument. Sitting across 25 billion transactions, 400 million accounts, and 30 million merchants, the network’s signal isn’t deep inside one retailer’s funnel — it’s horizontal across the entire purchase graph. That’s not a positioning claim. It’s an infrastructure reality. And it changes what retail media ROI actually means.

The Difference Between Deep Data and Wide Data

Most retail media networks — Lazada’s LazMall Ads, Shopee’s in-platform targeting, even Amazon’s DSP — derive their value from vertical depth. They know what you searched for, browsed, abandoned, and bought inside their ecosystem. That’s powerful for lower-funnel activation, less useful for understanding cross-category or cross-merchant purchase behaviour.

PayPal Ads’ Mark Grether made the distinction explicit at Cannes 2026, as reported by AdExchanger: the network can observe what a consumer buys at a travel brand and an electronics retailer and a food delivery platform — not because PayPal is scraping behaviour, but because it processes the actual transactions. The signal is deterministic, not modelled. That’s a meaningful difference when you’re trying to prove incrementality rather than correlation.

For brands spending in retail media across Southeast Asia — where consumers routinely split purchase journeys across Shopee, Grab, and direct brand apps — the ability to stitch that journey deterministically is the gap most networks cannot close.

Why This Reframes the ROI Conversation

The standard retail media pitch is last-touch attribution inside a closed garden: you spent here, they bought here, here’s your ROAS. It’s a number that’s both true and incomplete. It tells you about closed-loop conversion. It doesn’t tell you about the role your spend played in a purchase decision that concluded elsewhere.

Cross-merchant transaction data reframes the question. Instead of asking “did this ad lead to a purchase on our platform,” the question becomes “did this consumer’s broader purchase behaviour shift after exposure?” That’s incrementality measurement with actual teeth.

For advertisers running brand campaigns across the region, this matters beyond retail. If a fintech or FMCG brand in Indonesia or the Philippines can demonstrate that ad exposure correlates with measurable changes in downstream purchase behaviour — across multiple merchants, not just one — the conversation with CFOs changes. You’re no longer defending cost-per-click. You’re presenting purchase-behaviour shifts at scale.

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The Identity Infrastructure Underneath

What makes PayPal Ads’ model work is that payment credentials function as a persistent, consented identity anchor. The user doesn’t need to be re-identified across sessions or devices — the transaction itself carries the identity. No third-party cookie. No modelled audience. No probabilistic graph stitching.

This is the direction the industry has been trying to engineer toward since cookie deprecation accelerated. Clean rooms, universal IDs, data collaboration platforms — all of it is attempting to replicate what a payment network has by default: a deterministic, first-party, cross-context identity layer.

For Southeast Asian markets, this has particular relevance. Mobile wallet penetration is high and growing — GoPay, TrueMoney, GCash, and OVO each sit on transaction graphs that, if opened to advertisers in a privacy-compliant way, could power retail media products structurally similar to what PayPal is building. The infrastructure exists. The commercial and regulatory frameworks to activate it are the missing piece.

Separately, the broader question of who controls data provenance is getting sharper. Digiday’s recent coverage of SPUR — a publisher-run consortium building a Content Telemetry Framework to make AI’s use of publisher content transparent and licensable — signals the same underlying tension playing out in a different corner of the ecosystem. Whether it’s publishers asserting control over AI scraping or advertisers demanding proof of transaction-level attribution, the theme is identical: opaque data flows are losing legitimacy, and the players who can demonstrate clear provenance and consent will command a structural premium.

What Southeast Asian Brands Should Be Asking Right Now

If you’re running retail media budgets across Southeast Asia and your measurement framework still relies on platform-reported ROAS inside a single network, you’re measuring confidence, not reality. Three questions worth pressure-testing with your media partners:

First, what is the identity resolution methodology — deterministic transaction-based, or probabilistic modelling? The answer affects how much you should trust incrementality claims. Second, does the network have any mechanism to observe cross-merchant or cross-platform behaviour, or is the closed loop actually a closed box? Third, what does the data collaboration agreement look like — are you contributing first-party data into a clean room with actual controls, or signing a broad data-sharing clause buried in the MSA?

The retail media networks that will matter in 2027 are the ones building honest answers to those questions now. The ones that can’t answer them are selling reach with a measurement story bolted on.

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The gap between retail media’s promise and its proof has always been identity and attribution. Payment networks closing that gap deterministically isn’t just an interesting product development — it’s a signal about where the industry’s infrastructure is heading. The real question for brands in Southeast Asia is whether the regional platform ecosystems will open their transaction layers to power similar models, or whether that data will remain locked inside super-app walls that advertisers pay into but never truly see through.