We could not miss the news of acquisition of WhatsApp by Facebook, so we covered it in the recent post on HBR Blogging Network. With $19 billion, Facebook could have purchased Sony or Gap or four aircraft carriers. Instead, it bought WhatsApp, a tiny startup that so far had accumulated barely $60 million in funding, mostly from Sequoia. This is nuts, you might say; although the world of mobile messaging is upon us, that is an awful lot of money. But think about what exactly Facebook is buying: