https://techcrunch.com/2019/07/16/libra-in-messenger-whatsapp/

Facebook will only build its own Calibra cryptocurrency wallet into Messenger and Whatsapp, and will refuse to embed competing wallets, the head of Calibra David Marcus told the Senate Banking Committee today. While some like Senator Brown blustered that “Facebook is dangerous!”, others surfaced poignant questions about Libra’s risks.

Calibra will be interoperable so users can send money back and forth with other wallets, and Marcus committed to data portability so users can switch entirely to a competitor. But solely embedding Facebook’s own wallet into its leading messaging apps could give the company a sizable advantage over banks, PayPal, Coinbase, or any other potential wallet developer.