> 2% dropout rate per day on a quarantine period for all individuals flagged as contacts, which lasts up to 2 weeks. I don't know what they used to come up with that number for dropout rate, but it seems highly optimistic if the information about who has registered as a contact is kept private

Sorry but I don't understand how keeping contact information private or public has any effect on the compliance of people to stay in quarantine?

> So, my — non-expert — conclusion at this point is that privacy-preserving digital contact tracing probably isn't going to be that useful because people either won't use it or won't follow the advice when doing so is inconvenient (e.g. because it puts their employment at risk). But digital contact tracing in general seems like it can help, if you can drive both usage and compliance high enough.

I don't understand why you think an app that can promise to keep people's personal data private would gain lower adoption than one that was explicitly collecting such data. Maybe I've misunderstood what you're trying to say here but it would make more sense to me that an app that can preserve privacy would have higher adoption, higher trust and therefore higher compliance levels.