* Moving from folders to tags/groups means greater flexibility in contact organization for our users.
<b>5) Build an API for address book "contact providers", which allow read and write to various online contact services. ([https://TODO:FEATUREPAGE wiki.mozilla.org/Features/Thunderbird/Contact_Provider_API feature page]):</b>
* Design a contact editor that is flexible enough to deal with the variety of fields that a contact provider could require / support.
* Provide a way to display contact groups / mailing lists from contact providers as an address book group.
* Provide a mechanism for dealing with "mid-air collisions", or write conflicts for contact providers.
* Store contacts from a contact provider locally for offline searching / editing. Offline edits will need to be queued until connectivity is restored, at which time the operations will commence.