WhatsApp CEO Jan Koum announced this morning that the messaging service has now reached 900 million monthly active users, which is actually kind of funny when you consider the fact that the Facebook-owned company still doesn’t have a business model. To be fair, monthly active users is a metric that doesn’t matter very much to messaging apps, but it’s still an impressive number nonetheless, and it means that Facebook controls a significant chunk of the market for messaging apps when you combine the WhatsApp numbers with Facebook Messenger’s.