I learned something important from Walt Mossberg recently:

About a week after our launch, I was seated at a dinner next to a major advertising executive. He complimented me on our new site’s quality and on that of a predecessor site we had created and run, AllThingsD.com. I asked him if that meant he’d be placing ads on our fledgling site. He said yes, he’d do that for a little while. And then, after the cookies he placed on Recode helped him to track our desirable audience around the web, his agency would begin removing the ads and placing them on cheaper sites our readers also happened to visit. In other words, our quality journalism was, to him, nothing more than a lead generator for target-rich readers and would ultimately benefit sites that might care less about quality.

Walt is talking about cross-site tracking, in which an advertiser can see that a reader on one web site later visits an unrelated site. Same reader, different web site. This is the mechanism behind the “creepy” ads that follow you around the web from site to site.

It’s striking how up-front the advertiser is. He likes the web site, but he’s not interested in supporting it, just using it to get data that he can use on other, cheaper, lower quality sites. He has no concern for the publisher; content is just a commodity.

This is clearly a terrible deal for any publisher trying to build up a valuable audience with quality content. Walt’s headline is Lousy ads are ruining the online experience, but I think it should have been something like Publishers are harmed by cross-site tracking and should not allow it.

If cross-site tracking harms publishers then they should push back. As a technologist I know that there is no easy technological solution that can prevent tracking; at best it is an arms race that publishers are ill-equipped to wage. Technology is not the solution. What is needed is a social contract.

Fortunately, publishers know how to negotiate contracts. With advertisers, they negotiate the appearance and content of ads, and they put conditions on how intrusive the ad can be. They can, and should, negotiate an end to cross-site tracking. They should refuse to run ads unless the advertiser agrees not to track their readers on other sites. That is, data from their own site should not be correlated with data from other sites.

There is one technology that I suggest publishers use: referrer policies. When a reader clicks a link on a web site, the new web site by default gets to learn where their readers are coming from: they get a “referer” header that includes the linking web site. Obviously this allows cross-site tracking. Publishers should consider using referrer policies to change this default and prevent cross-site tracking.

Ultimately, however, social norms and not technology are the only solution.