Just because something doesn't work well when done right, doesn't mean it should be done wrong. There are ways to gather data necessary to inform product decisions without surveillance, or turning your users into non-consenting test subjects.
(EDIT: Nevertheless, I'm very happy about the values they describe and that they chose to store the data locally. It makes me trust the authors that much more, and conversely, if it wasn't local, I wouldn't even consider using it.)
At the moment analytics are turnt off, but in general we only do telemetrical analytics. So we only track the way you interact with the software, like the buttons you click, to optimise user flows. We don't ever send anything that is user generated content, like tags, annotations, visited urls or anything that can be considered your personal knowledge.
More you can see here: http://worldbrain.io/privacy
Yes indeed we will be a regular SaaS business, but with a strong focus on privacy, data ownership and interoperability. More can be found here: https://community.worldbrain.io/t/why-worldbrain-io-does-not...
Initially our services like Sync and Backup will only be available for the premium upgrade, but our infrastructure is already built in a way that allows making it self-hostable too. It's just a matter of resources we have available. We very much value your data sovereignty but we first need to make enough money to be able to continue development and have enough time and money to make it self-hostable. It's all a bit more difficult without raising VC capital (see link above).
They charge for synchronization and backups, with no doubt more to come.