Interesting development. However, in reality this highlight's Facebook's weakness – lack of focus on what it is. Twitter is a dedicated microblogging infrastructure. Facebook is not and simply adding a way to do microblogging within Facebook does not make it such. No one is going to sign-up to Facebbok to do microblogging. A better strategy would be to make it possible to 'do' Twitter from Facebook rather than 'be' Twitter.