Marketers — are you training your competitors' ads?

A funny thing happened to me the other day. I was working on a video project on my laptop and I went on the Viking Cruises website (vikingrivercruises.com.au) to grab an image I needed. The image related to a Christmas Market Cruise we took down the Rhine last year (p.s. I highly recommend it!)

I got my screenshot, worked on the project and a while later, took a break. I was scrolling on Facebook on my mobile, when lo and behold I got an ad for a European Christmas Market River Cruise. But what caught my attention was that it was not an ad for Viking Cruises — as you might expect — but for Avalon Waterways. If you're not familiar with the category, Avalon and Viking are separate companies and direct competitors in the premium river cruise market, primarily in Europe and Asia.

Having worked in online advertising for a long time (and in travel specifically for 3 years) I realised I had just witnessed an event that marketers sometimes miss.

I suspect my visit to Viking triggered an advert for their competitor on Facebook. In all likelihood, Viking have Meta tracking code on their site (Ghostery confirmed this) and a signal was sent into the Facebook advertising network that said — "hey, here's a prospect for a relatively expensive travel product, let's light up the ads that are most relevant to this guy."

It's an active category and within a few hours I saw ads from Viking, Ama Waterways, Avalon and others.

We all know what that's like — being stalked by ads after displaying a casual interest in a topic. (PS Just Jeans — I bought those black 511's months ago — please stop retargeting me!)

What Tracking Code Actually Does

One of the main tenets of performance advertising over the last decade is that you must put code from third-party providers on your site to better measure the impact and effect of your media spend.

In Meta's case the code is called the Meta pixel. This code snippet is sold primarily as a first-party measurement and optimisation tool — allowing marketing teams and agencies to track conversions, build retargeting audiences, and optimise campaigns. Most marketers understand it at that level.

What Else Is Happening

When a client installs the Meta pixel, they're not just collecting data for themselves. The pixel feeds Meta's broader data graph, which powers the entire advertising ecosystem.

This means:

• Event data trains Meta's models globally, not just for that advertiser's campaigns. A retailer's conversion signals help Meta understand purchase intent signals across all advertisers.
• Audience insights are pooled. Meta uses behavioural signals from across the web to enrich its targeting capabilities for every advertiser on the platform — including competitors.
• Competitors can target customers you might consider "yours" using Meta's interest and behavioural segments that were partly built from signals your pixel contributed to. They don't get your customer list, but Meta can identify and model people who look like your customers and sell that reach to anyone.

To be clear, when a client signs up for the service, the corollary is included in the fine print: the signals will feed into the Meta ad signal network.

But marketers would be forgiven for missing this, as the documentation and sales narrative keeps the framing firmly on "improve your own performance."

In my own dealings with Meta, when I sought information on this for a client, they were at pains to point out that one visit to a client's website does not trigger an ad for a competitor. The system operates more broadly — a person would need to read content about river cruises, perhaps like a post on Facebook, search on Instagram for content, before the targeted advertising kicks in.

But yes — if a person enters a relevant targeting segment, any advertiser with an active budget and creative can bid to put ads in front of that potential shopper.

In some ways it's a beautiful thing, exploiting the power of the network. Standalone publishers supported by advertising can only dream of such things.

A Pulse Check on Trackers

I have been out of the agency side of the ad industry for a couple of years. I wanted to take a pulse check on trackers and so I've drawn on Claude AI to do a deep dive into the topic, which I've included below as a download for marketers.

The usual clauses apply. I've checked the sources and applied as much human oversight as possible, but I would be happy to correct any errors or omissions. Also, this is written from a personal perspective on a subject I am interested in and does not reflect the views of any organisation I am associated with.

I asked Claude to look at three platforms — Meta, TikTok and Google — and answer three questions:

• What is the code the platforms ask to be implemented?
• What is the stated benefit for the marketer?
• What is the ancillary benefit for the platform?