Being business orientated LinkedIn wouldn't get to same amount of publicity as a social network, that's not to say it isn't a very big network.. They have 433 million members, that's a pretty decent and marketable number if you ask me..
For Comparison WhatsApp has 500 Million users.
Instagram has 300 Million.
Twitter has 974 Million (Most of which are spam accounts lol)
Facebook has 1.1 Billion ... Siigghhhh