WhatsApp now one-third the size of Facebook

WhatsApp now one-third the size of Facebook

CNET: Mobile messaging app WhatsApp now has more than 400 million users each month.

The startup has added 100 million new active users in the past four months, CEO Jan Koum wrote in a blog post.

"WhatsApp has just 50 employees, and most of us are engineers. We've arrived at this point without spending a dollar on targeted ads or big marketing campaigns," Koum touted.

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