I think without having a select all option, the contacts picker is going to be futile for most use cases. I believe it is imperative we allow users to select all contacts unambiguously with the right permission prompt of-course (and unselect those that the user wants to opt-out) as the contacts import flow is usually a one-time action, part of an on-boarding flow or discover people flow in most social apps (Twitter, Pinterest, Facebook & Instagram)

Without having a select all option, this API adds no value to improving UX and helping users find the right people to connect with. I would also suggest a default mode all contacts pre-selected, behind a strongly worded permission prompt. The goal here is to reduce the number of inputs that the user has to make to achieve the ideal result.

In the context of using the contact picker in an email application - I think most email apps will do a better job auto-completing than having to select individual contact info via a picker. The feels more like finding a solution for a problem that doesn't exist :) Even here the core use case would be to import all contacts and then optimize autocomplete.

Thoughts?