Evans also computes that WhatsApp has 430 million active monthly users, not bad for a company that has just 50 employees and has never spent one penny on advertising or promotion. Consider that back in April, Google allegedly offered $1 billion for the messaging app and that was well before WhatsApp had the kind of numbers that it has now.
Check out the chart below, which was tweeted by Evans, and you can see the phenomenal growth trend that WhatsApp is on.
WhatsApp is riding an amazing growth trend
source: @BenedictEvans via BGR