Defaults is what matter, as you can nudge users either way. Any (binary) choice by the user is influenced by the default. It's all a [[Everything is a Binary Classification Problem]]. Opt-in creates more false negatives, opt-out more false positives. You have to understand base rate of people who would want it, cost of false negative, and cost of false positives. For example, if you're onboarding on a new phone, and asking the user whether they want it backed up to the cloud, opt-out is a reasonable approach. If you're about to sell something to the user, and there's a possible add-on, then opt-in is the correct (and legally mandated) approach. #published 2025-01-25