BlackBerry has announced that it will bring its BlackBerry Messenger (BBM) platform to iOS this summer. BBM was one of the first proprietary mobile messaging services -- not unlike Apple's iMessage service -- and remains hugely popular. The company reports that BBM has 60 million monthly active users and that BBM users send 10 billion messages per day. In January, Apple claimed iMessage users were sending 2 billion messages per day. Moreover, there are a number of popular so-called 'over-the-top' messaging services including
