WhatsApp provides phone-number-based messaging, and people asked, 'Isn't that what SMS is?' Yes, but SMS is expensive, antiquated, and what WhatsApp did was modernize and level that playing field. For example, in Europe, if France wants to talk to Belgium, it's extraordinary costly because of border and telecom charges.
There's a certain degree of speculation that goes into valuations. In so far as the market supports a valuation, everyone who gets a great one deserves it, but they should also be cautious because that speculation is temporary. I saw Yahoo go from $100 billion to $10 billion. It's not a long-term measure.