The biggest unanswered question about Apple and Google’s coronavirus tracker

On Friday, Apple and Google announced an unprecedented project to track and halt the spread of the novel coronavirus — and we haven’t stopped talking about it since. The project would use bluetooth signals to track who participants have been in contact with, potentially providing an automatic, anonymous form of contact-tracing. It’s been messy, but a lot of the major questions have been answered, although there’s one lingering one that hasn’t.
But let’s start