It is perfectly easy for other web services to access the data of a logged-in Facebook user, provided that the user has granted permission via Facebook Connect. This is how Facebook's "Download your Data" product[1] works; it is entirely implemented through publicly available graph APIs.

What Google is insisting on is "download my friends' data." This is where Facebook currently draws the line; we make it easy to retrieve your own data programmatically, while retrieving your friends' data programmatically is harder.

And, whatever Google says, Facebook is right to draw the line somewhere, and probably at friends' contact info. Consider an immediate consequence of doing what Google is insisting on: Zynga (e.g.) will spam all of their users' friends' emails. Because now they can retrieve them in bulk via a Facebook API. If you use Facebook, and tomorrow you started getting reams of email from applications you do not use, would you think, "How wonderful that Facebook has finally liberated my data!"? Or would you, maybe, be annoyed, and wonder why Facebook would ever consider making such a boneheaded decision?

[1] https://register.facebook.com/editaccount.php -> "Download your Information"