Changes

|Feature open issues and risks=* Syncing across a variety of contact providers presents a challenge when those contact providers don't necessarily share support for the same fields.

** As an example, consider the Google Contacts interface via GMail. This interface allows us to add an arbitrary number of phone numbers to a contact, and to give those numbers labels. Those labels are either predefined (Home, Work, Fax, etc) or can be set to a custom value. Microsoft Outlook 2010, conversely, does not give us an affordance for creating a contact with more than 14 phone numbers, and the labels cannot be customized. So what happens when a contact with phone numbers with custom labels gets sync'd? While this might be an edge case, since this involves a user's data, we should really think through what we would do.

|Feature overview=From a surface perspective, Thunderbird's address book has not changed much since it's very beginnings. Even today, by default, it is impossible to create a contact with more than 2 e-mail addresses in Thunderbird. It has also failed to adapt to the social web as it exists today, where the identity of contacts can be spread across multiple services (Facebook, Google Contacts, LinkedIn, Twitter, LDAP, desktop address books, etc). It also has no notion that contacts may belong to one or more groups.