This new API provides access to one of the largest collections of address books on the Internet--the contact system behind Yahoo! Mail, Yahoo! Messenger, and Yahoo! Go. This means your applications already have a built-in audience. The Address Book API supports a wide range of third-party apps, such as sending invitations to seed social networks or social apps, looking up postal addresses for shipping services for online retail, and providing address "auto-complete" for messaging apps.
The API has extensive search capabilities. Once a user authorizes your application, youíll be able to easily access that userís address book and look for specific contacts. If you want to see which contacts are new, you can ask whatís changed since the last time you accessed the API.