Slack is a direct successor of IRC. Those who are familiar with the IRC are quickly getting used to. But if used by people without IRC experience, the result usually suffer as they don't understand the IRC culture and can't use it efficiently. I've heard a company failed so bad at using slack. Only the sysadmins has the privilege of creating the public channels, resulting just a handful of generic use channels and most channels are flooded with noise. To reduce the noise, they ban the non-essential post to the Slack, just nullifying the Slack as a communication tool.