Making birthday greetings on Facebook even more impersonal, the social networking giant has rolled out a feature that allows a user to wish "Happy Birthday" just by texting '1' from a smartphone.The new feature works for those who have Facebook notifications pushed to their text messaging programmes, Tech Times reported.The feature is part of Facebook's SMS notification functionality, which allows users to interact with friends through text messages.So with this feature, you receive a message that one of your Facebook friends is having a birthday today.And to leave a "happy birthday" message on their wall, all you have to do is reply with a text that says "1".While the feature makes wishing your friends on their birthdays easier, it risks conveying your feelings in a very impersonal manner.