Interesting metrics and insights.  Another tidbit, WhatsApp rivals SMS for daily messages sent. 

Wow I didn't realize WhatsApp is as big as SMS!

http://www.dailyfinance.com/2014/02/21/facebook-whatsapp-buy-highlights-telecoms-texting-problem/

Free social-messaging applications like WhatsApp cost phone providers around the world -- from Vodafone to America Movil (AMX) and Verizon (VZ) -- $32.5 billion in texting fees in 2013, according to research from Ovum Ltd. That figure is projected to reach $54 billion by 2016.

They are hurting the SMS providers $32 BILLION per year, up to $54 BILLION by 2016. 

Do they make it up with more links to web, consuming more bandwidth?

Sweet summary of the deal to beat all deals!

Thank you Geege!

Between this and Instagram, I learned that user/engineer ratio is an important metric if you want a large exit/valuation.

Which makes no sense. In general, the more great engineers, the better it is for the company, since, you know, the engineers actually build things.