A large number of people are playing this, but there are so many game modes and rooms that each map has about 2-6 human players, the rest filled with bots. Yes, the game is popular (not massively, true, but popular), however a large foundation with so many room possibilities makes it seem very sparse.
Remember this, when a player leaves, another player from a 1-Human 9-Bots room isn't brought over. Another bot is simply added until a new human jumps in. This leaves a lot of fragmented rooms with a generous mix of humans and bots.
PSN - LonestarGoner - Bow before the great and mighty King of Trolls, for I shall command your emotions and bend your anger and revulsion to my whim!