This is not entirely true. A Facebook application can get an email address of an authorized user by requesting it [1] (in the authorization dialog, the user can choose to send the application either the email address they signed up with Facebook for, or a proxied Facebook email address). There is currently no way to use the Graph API to retrieve your friends' email addresses.

[1] To do this, your application has to request the email permission. There is no equivalent friends_email permission. See http://developers.facebook.com/docs/reference/api/permission...