whatsApp history
Koum then hired an old friend who lived in Los Angeles, Chris Peiffer, to make the BlackBerry version of WhatsApp.
WhatsApp was switched from a free to paid service to avoid growing too fast, mainly because the primary cost was sending verification texts to users. In December 2009 WhatsApp for the iPhone was updated to send photos. By early 2011, WhatsApp was in the top 20 of all apps in the U.S. App Store.
The founders agreed to take $7 million from Sequoia Capital on top of their $250,000 seed funding, after months of negotiation with Sequoia partner Jim Goetz
By February 2013, WhatsApp's user base had swelled to about 200 million active users and its staff to 50. Sequoia invested another $50 million, valuing WhatsApp at $1.5 billion.
On February 19, 2014, Facebook acquired WhatsApp for $19 billion (see Acquisition below).
In April 2014 WhatsApp crossed half-a-billion user mark