From Facebook Developer Wiki

"If the user's age is hidden for privacy reasons, Facebook still determines whether or not the application is visible to the user"

"However, if the user's age is hidden for privacy reasons, Facebook cannot determine whether or not the content is visible to the user"

This two statements contradict each other. Which one is true?

They're both true; one is at the application level, the other is at the level of specific content within the application. Facebook always knows the user's age, since that information is provided when a user signs up for Facebook. If a user has chosen to hide his or her age from public view, Facebook can use this setting to determine whether or not that user can even see an application that has a given set of demographic restrictions on it.

However, if a user who has hidden his or her age from public view has authorized an application, the application cannot query for the user's age, and so the tag can't be used to tell whether or not to render the content. This is just another aspect of user privacy. -- Pete (563683308 13:29, 1 December 2008 (PST))

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How does age restriction work in case of receiver? Will a sender who is 21 be able to send a beer to someone who is not 21 assuming they already have the application installed?

It works the same way -- if the you have the restrictions set at the application level (with the API call), the receiver will never see the application (and never be able to authorize it). If you have the restrictions set at the content level (with the FBML tag), the receiver will only see the contents of fb:else, which is why it's really important to have an fb:else statement. See the first note in the Description at fb:restricted-to. So, no, an underage receiver will not be able to receive the beer. Does this help? -- Pete (563683308 18:00, 3 December 2008 (PST))

Thanks Pete, that helps

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The allowed_restrictions users table column is still completely unreliable. Discussion at:

http://forum.developers.facebook.com/viewtopic.php?id=28638

Thanks for bringing this to our attention. I reported the issue to the relevant people internally but if you could file a bug it would help us track the issue. Thanks -- Pete (563683308 19:18, 16 February 2009 (PST))