That's only if you believe that Whatsapp is worth $19B (which I don't). If it's not worth $19B, then it's Facebook throwing away $4B cash and diluting themselv

That's only if you believe that Whatsapp is worth $19B (which I don't). If it's not worth $19B, then it's Facebook throwing away $4B cash and diluting themselves for $12-15B. Companies FB could have bought for around $20B: Linkedin, Whole Foods, Broadcom, The Gap, etc. There is no sort of metric that makes sense to purchase this product for $19B. Even if every user paid $1/yr, that's paying $19B for $450M revenue stream, or 40 times revenues. It's insane.