According to a developer they were originally planning on having 32 player multiplayer then experimented with more and had it up to 73 but eventually settled on a managable 50. It'll be interesting to see how well it plays with that many players when it's released.
Source: (Developer on their official forum)
http://community.kaosstudios.com/showthread.php?s=51bf8e994b4be7a8ab36495b0283702e&p=45435#post45435










