importing your address book from other services?

[xpblueScreenOfDeath]

Does anyone know how the social networking sites are importing address books from popular online email accounts? They ask for your email and password and then they are able to retrieve your address book. And if you want they will invite your friends to join. How are they doing? Does anyone know of an API that gmail, yahoo, hotmail, and aol provide or how it is done?

 

[jpadie]

for gmail, at least, the API is published.