“There are several improvements in themes,” said Hamed Haddadi, chief scientist at Brave, a privacy-focused browser and search engine. He says that with FLoC, people could be grouped into more than 30,000 different categories, which would allow advertisers to gain specific knowledge about their interests. This information can then be combined with other data to build an incredibly detailed picture of each of us.
This is less likely in topics, as there are about 350 interest categories that can be assigned to people. Although that number is likely to increase – Google’s whitepaper says that its ultimate goal will be to source these third-party themes, and there could be “several thousand themes”. Haddadi also says that adding a sixth random topic to people’s interests makes the system a bit more privacy-conscious.
Another potential difference between FLoC and Topics is that Google says the latter will try to avoid assigning “sensitive categories” to people — such as allowing individuals to be shown ads based on their race or gender. FLoC has been criticized for potentially generating or inferring sensitive attributes through people’s behavior and interests. Google says people will get more control over the areas of interest assigned to them and will be able to change settings, block topics and opt out in Chrome. But realistically, it’s unlikely that many people will change Chrome settings this way.
Moreover, the risk of websites revealing one’s sensitive personal traits is not completely removed by themes. “It is still possible for websites calling the API to combine or match themes with other signals to expose sensitive information beyond their intended use,” Google’s description of themes says. Over time, it would be possible for the site to “develop a list of topics that are relevant to this user,” and this could reveal sensitive information. There are other privacy and security issues that Google says need to be fixed. Google plans to test themes in Chrome in the coming months, and the system may change based on feedback.
Then there is the problem of competition. The smaller number of interests assigned to people could potentially give Google even more power in the online advertising industry it already dominates. Paul Bannister, co-founder of ad management firm CafeMedia, says Topics appears to be a step forward for people’s privacy, but a potential step back for advertising firms. The 350 current interests included in Topics are broad, Bannister says, and that means they’re less likely to be useful to advertisers trying to target people with products they’re more likely to buy. “These topics are fixed, so it’s harder to find unique segments that are really interesting for your marketing campaign,” he says.
