Facebook didn't pay so much for an app. Facebook paid so much for the users that are using it. The users and their data is the product.
^^ This. FB paid $19b for 350million - 490million (depending on which source you read) user assets. The app means nothing to them, I mean come on they already have facebook messenger right? FB must have the in-house development skills to clone WhatsApp in a week. But for a business who's sole purpose is to profile people for advertising $$$, slurping all those extra contact lists and mobile phone books for "who knows who" is where the value was in that deal. And given that Bitcoin, by design, protects user anonymity with no centralized userDB, the two things don't make a suitable comparison. They placed that value on WhatsApp in terms of something like $45 per user, not the app, code or service itself. IMHO.