A more sophisticated approach uses Facebook’s Open Graph API to retrieve the Likes and interests of the user, as well as those of his or her friends. There is a permission screen involved and every friend’s privacy settings are individually respected.
For the past few months Amazon.com has been offering a “Tap into Your Friends” option (still labeled Beta). After the permission screen, the user is taken to an Amazon page showing the upcoming birthdays of Facebook Friends and their Amazon Wish List if they have one. Amazon uses a user’s friends’ profile data, which often includes favorite books and music, to make gift suggestions.