For me it's not a deal breaker (in fact Muse looks awesome and I'll be checking it out soon!) but is a bad smell that could be a deal breaker if there's other t

For me it's not a deal breaker (in fact Muse looks awesome and I'll be checking it out soon!) but is a bad smell that could be a deal breaker if there's other things that feel off. Don't know if this applies to others who say it's a deal breaker, but I have a grasp on my own psychology. If an email is required and not optional, it's because the service/provider needs it for the service to work. If I'm using an online service providing my email is obviously for reasons that make my own experience better. If using an completely offline app, there is no clear way it makes my own experience better, so it must be entirely for THEIR benefit, which brings up what they're doing with that data. As a user when being introduced to a new product it's like meeting someone new and picking up on subtle social cues and deciding if they are trustworthy or not. As a founder myself I know being able to identify users can benefit them. It's also irrational that signing up for an online service bypasses this gut check. However psychology is rarely rational.