The ethics of retargeting ads that follow users across devices

A shopper browses a pair of running shoes on a mobile phone, compares prices on a work laptop, and later sees the same product promoted on a connected television. This sequence is now familiar across digital advertising. Retargeting can make marketing more relevant, yet cross-device tracking raises a harder issue: whether people understand how their behaviour is being connected and used.

The commercial appeal is clear. Advertisers can reconnect with visitors who abandoned a cart, tailor creative to recent interests, and measure campaigns across websites, apps and streaming services. The ethical question is whether this convenience is purchased with an invisible loss of privacy, autonomy or control.

For Australian marketers, the debate sits within a changing privacy environment shaped by the Privacy Act, the Australian Privacy Principles and growing public concern about data brokerage. It also belongs in the wider conversation about responsible contemporary marketing, the kind of research and professional exchange associated with ICCMI 2019 and its academic and business audience.

Why cross-device retargeting feels intrusive

Retargeting across devices depends on identity resolution. A platform may connect a browser cookie, mobile advertising ID, login, email address or probabilistic signals such as location, device type and browsing patterns. The result is a profile that can recognise a person as they move between screens, even when no single device reveals the whole journey.

This process is often invisible. A consumer in Melbourne may search for flights on a personal phone, read reviews on a desktop and later encounter an advertisement in a social media feed. The person may never have knowingly agreed to a company combining those activities. A privacy notice that mentions “partners” or “relevant advertising” may be legally available but practically difficult to understand.

Intrusion also depends on context. An advertisement for ordinary household goods may feel harmless, while repeated promotions for fertility treatment, financial hardship services or medical products can expose sensitive inferences. Even when the underlying data is technically non-sensitive, its combination with browsing history can reveal intimate details.

Consent requires more than a hidden setting

Ethical consent should be informed, specific and capable of being withdrawn. A preselected box, a confusing cookie banner or a long policy written for lawyers does little to establish meaningful permission. People need to know that their activity may be linked across phones, computers, tablets, apps and televisions, and that this information may be shared with advertising intermediaries.

Australian organisations should distinguish essential analytics from behavioural advertising. Someone who accepts a shopping cart cookie has not necessarily accepted a persistent profile used for cross-site and cross-device targeting. Clear choices can explain the purpose, categories of data, retention period and types of partners involved without forcing users through a maze of screens.

The principle also applies when data is collected through a loyalty programme. A customer using a Woolworths or Coles rewards account may expect discounts connected to purchases, but that expectation does not automatically extend to matching shopping behaviour with unrelated browsing activity. Consent should reflect the actual use, not merely the existence of an account.

Good customer communication supports this standard. Brands developing automated service channels can examine chatbot customer experience alongside advertising practices, since both rely on explaining data use in language people can understand.

Relevance must not become manipulation

Personalisation has legitimate benefits. A retailer can stop showing an item after it has been purchased, offer a useful size guide, or remind a customer about a product left in a basket. Frequency controls can reduce wasted impressions and prevent a campaign from becoming an unwanted presence across every screen.

The ethical boundary is crossed when relevance is used to exploit vulnerability or narrow a person’s choices. An algorithm might identify someone as likely to be desperate for credit, worried about their health or under financial pressure. Targeting that person with urgency, hidden fees or emotionally loaded messages can turn behavioural insight into manipulation.

Australian law already places limits around misleading or deceptive conduct under the Australian Consumer Law. Ethical marketing goes further by asking whether an advertisement takes advantage of an information imbalance, even when its wording avoids a clear legal breach. A limited-time offer repeatedly shown to a user who has not consented to intensive tracking may be technically effective while still undermining informed choice.

Advertisers should also test for discriminatory outcomes. Cross-device profiles can produce different prices, offers or access to information based on inferred income, suburb, age or household status. A campaign running in Sydney, Brisbane and regional New South Wales should be reviewed for unequal delivery, especially where automated bidding prioritises audiences that appear more profitable.

Data minimisation strengthens trust

The safest cross-device strategy is often the least expansive one. Companies should collect only the information needed for a stated purpose, retain it for a defensible period and avoid combining datasets simply because the technology makes it possible. Aggregated measurement, contextual advertising and first-party insights can sometimes deliver useful performance without following individuals across the internet.

A responsible programme should map every handoff: the brand, media agency, demand-side platform, data broker, publisher and measurement provider. Contracts need clear limits on reuse, onward disclosure, security and deletion. A vendor that promises precise audiences should be able to explain the source of its signals and the safeguards applied when identities are inferred.

Transparency must include practical control. Users should be able to opt out of personalised advertising, reset identifiers, delete accounts and access relevant information without unreasonable effort. Preference centres should work consistently on mobile and desktop, rather than requiring a person to repeat the same decision on every device.

Security matters because an advertising profile can become valuable to criminals and intrusive to employees or contractors. Strong access controls, limited internal visibility and timely deletion reduce the consequences of a breach. Privacy should be treated as a governance responsibility, not a minor configuration choice left to a campaign team.

Measuring responsible marketing outcomes

Performance metrics can encourage excessive surveillance when success is defined only by clicks, conversions or return on ad spend. A campaign may produce strong numbers because it repeatedly reaches people who were already likely to buy. This can disguise wasted impressions and reward increasingly invasive profiling.

Measurement should include incrementality: whether retargeting caused an additional purchase rather than merely receiving credit for one that would have happened anyway. Teams can compare privacy-preserving control groups, monitor complaint rates, measure opt-out patterns and track exposure frequency. These indicators reveal whether relevance is creating value or simply increasing pressure.

Governance works best when ethical review happens before launch. A cross-functional group involving marketing, legal, privacy, security and customer service can assess data sources, audience exclusions, sensitive categories and likely user expectations. Plain-language documentation should record why a particular signal is necessary and how the organisation will respond to misuse.

Public communication is part of accountability. When a brand wants media attention for a new advertising capability, its representatives should be prepared to explain safeguards rather than promote precision alone. Guidance on pitching to journalists is useful here because credible coverage depends on a clear account of benefits, limitations and evidence.

The Australian market rewards brands that respect relationships over time. A Myer shopper, a Bunnings customer in Perth or a small-business buyer in Adelaide may accept relevant communication while rejecting surveillance that feels secretive. Trust is a commercial asset, but it is earned through restraint, candour and consistent control.

Marketers, researchers and business leaders can turn these principles into action by auditing cross-device vendors, rewriting consent notices, limiting sensitive targeting, testing frequency caps and publishing clear privacy choices. Use the ICCMI 2019 community as a starting point for serious discussion about evidence-based, human-centred marketing, and make every retargeting decision accountable to the people behind the data.