Recommendation engines based on tracking individual users' behavior will always be dangerous. They are fatally flawed and not beneficial to humanity, even if they are free software and publicly audited. They inevitably result in someone invisibly controlling many others as they are in the process of thinking. That said, they will always be with us, so we must push for regulation of how they are used. The standard #Mastodon experience does not use such algorithms, but they are coming soon.