The strong-arm approach on display here is emblematic of Facebook's new app strategy, and its most aggressive play for mobile yet.
Pretty soon, if you want to send or receive a Facebook message, you won't be able to do so from the standalone Facebook app on iOS or Android. Users are reportedly receiving alerts from the social network, warning that they won't be able to click over to the messaging tab to chat with their friends. They'll have to download the Messenger app separately.