When passing email addresses through Facebook apps, it seemed possible to pass @proxymail.facebook.com email addresses instead of the registered email address.

・Reference: Facebookのアプリやゲーム経由でスパマーにメールアドレスを漏らさないようにするには？ | 適宜覚書-Fragments

It seems this was possible with the previous Facebook app specifications, but became unavailable after specification changes?

(Information as of 2012/07/07)

That’s all from the Gemba.