According to a post on the WhatsApp blog, “We are proud of this milestone, and we’re humbled by the extraordinary ways all of you have used WhatsApp. Whether it’s sharing vital information during natural disasters or health emergencies, finding a date, growing a small business, buying an engagement ring, or seeking a better life – we’re honored to be a small part of what people are doing to make their lives and the lives of those around them better.”
That being said, the number of users also seems to coincide with the number of active users the platform has. According to a recent Facebook community update, it was revealed that there are about 900 million users on WhatsApp each month, so it looks like the gap between active users and number of actual users is closing.
In fact a couple of years ago when Facebook announced that they were going to acquire the platform, Facebook CEO Mark Zuckerberg believed that the platform could eventually hit 2-3 billion users, and back then they only had 500 million. By hitting 1 billion, it looks like WhatsApp is about halfway to their mark.