Instagram, the Facebook Inc. FB, +1.09% photo-sharing application, announced in a blog post Tuesday that it has passed 400 million users. The announcement comes less than a year after the service announced that it had topped 300 million users, and Instagram said that more than half of the last 100 million users to join the service live in Europe or Asia. The user number can't compare to Instagram's parent company -- Facebook reported 1.49 billion monthly active users in its most recent quarterly earnings report -- and also comes in behind two other Facebook mobile properties, WhatsApp and Messenger. Facebook shares fell 2.7% Tuesday to close at $92.96. http://www.marketwatch.com/