So sharing email id with third party Facebook applications is not a good thing. But without sharing email id how to access Facebook apps and games that insist on email address sharing?
Facebook has a very useful and little known feature that lets you create an anonymous email id whenever you want to authorize an app or game. You can generate the anonymous email id by click on Change link while authorizing an app (see the screen grab below)
When an anonymous email is chosen while authorizing, Facebook hides your email id and shares the anonymous id with the app. This anonymous email id acts as proxy between you and application. Whenever application sends an email to the anonymous id, Facebook automatically redirected the mail to your mailbox. This way you can save your privacy. via labnol.