The new initiative was announced this morning and will go live today. Developers can now request user e-mail addresses during the initial authorization process (which they can make optional or required), Facebook will extensively promote the feature on every application page users visit, and users can either share their actual e-mail address or a Facebook proxied e-mail address for anonymity.
How it Works
On the surface, user e-mail sharing is just another extended permission that application users will be able to allow (or not) during the authorization process. For the user, this means that the process will flow similar to other application requests that they can accept or reject during authorization.
Here's how it looks if the developer chooses to make e-mail sharing optional:
And if the application requires your e-mail address:
Given that Facebook wants to make full transition from application-to-user notifications to direct-to-user e-mail communication, it plans to promote the change extensively.
As an application user, you'll start to see dialog boxes at the top of every application canvas page you visit. You'll see these for the next three months or through three independent sessions with a single application.
You'll probably get pretty familiar with dialogs that look similar to this:
What It Means
For developers, the big e-mail push by Facebook is huge in terms of connecting directly with their application users, something that most have only been able to do indirectly up until now. Essentially Facebook will no longer serve as the middleman between you and your users.
For sites that leverage Facebook Connect as an alternative login, it's also an important development that will help you store new member e-mail addresses, or the proxied Facebook e-mail address, for future contact.