I Thought Facebook's WhatsApp Deal Was Crazy. Then I Did Some Math.

[Commentary] There's no disputing that Facebook paid a huge premium for WhatsApp, an untested company in a hotly competitive communications sector. But it takes less than I thought to turn WhatsApp into a decent, if justifiable, business. And that doesn't even count other benefits of scale, strategic defense and Google-rattling that are harder to quantify. Here’s the most obvious and powerful of Web dynamics: Massive global reach at nearly zero marginal cost. Up close, it can be majestic.