In that scenario, not going opt-out is not a mistake. But going opt-in probably is a mistake, because the data will be useless, so it’s a waste of time to implement.
The entire idea is bad, the defaulting reduces the impact to many but the very existence of this telemetry is enough to take more significant security defence against the tool. Once you start doing that as an organisation Go becomes legacy with a strong desire to replace it. Its definitely a mistake to make it opt in, the data will be lower quality and it will still drive security concerns.
Not true. The code is open source and everyone can trivially with minimal effort check that they are sending only the data they said they would send.
So if someone says that opt-in data is useless, I'd say that out-out data is just as useless.
And then we have to pretend that implementation, collection and analysis and then further actions would make it worthwhile.
Googler 2: The data says 100% of users are opted in, so deprecating the obsolete and unpopular opt-out functionality is the evidence-based choice. Ignore the shrill demagogues on the mailing list saying otherwise, their anecdotes are meaningless.