That could be done locally, without sharing the private data. The local computing agent can then look up in the public (like the pool of those who deliberately published content for all to see) for information that may be of interest to the user. That would have been a moral solution to please everyone. What we see happening now is a nightmare!

It could be done locally, but in order to not share any data with the server you'd need to run the analysis (with all of the associated data) on the local machine, which unless I'm missing something would add some non-trivial constraints, e.g.

- Getting research-grade analysis code up to local-install quality levels, keeping that code updated

- Bandwidth and HDD space for large datasets

- The additional load on the CPU, memory, battery, and messaging that to the customer

- The legal and privacy implication of all that opt-in data being transferred and processed on thousands of opt-out customers' machines

- The need to have an entirely duplicated system because some people would rather opt-in and not have to run all this stuff run on their already-creaking-under-the-weight-of-windows-and-outlook-and-word-and-antivirus laptop

Maybe I'm misunderstanding something, but from this view I can understand why they didn't want to do it this way

Those improvements could be done with much less intruding anyway (be it for the sake of it or because johnny hacker is going to release those data someday).

Sure, although user happiness (broadly) drives market share so they need to maximise that to maximise profit.