Genuine question: If the network is decentralized, how are they able to determine the amount of users on the system?
The article mentions opt-in usage reporting, but that would only indicate there's around 115 million users actively reporting that they're using it, right?
Agreed. And in a way, it is also a contributing factor to how polarizing internet-based discussion has become. Rather than show you the most cited websites for answering a political question, it's going to use its profile of "you" to show you something you're more likely to engage with.
It reminds me of a story that a web developer who found out that other sites were hosting his game by linking back to his website in an iframe and using it to make money off of ads. He made a check that if any calls are being made to the game from an iframe, replace the game with an image of goatse.
https://www.pcgamer.com/websites-stole-and-monetized-a-free-browser-game-so-the-designer-replaced-it-with-goatse/