You are right, a lot of companies would walk away from that pretty quickly as long as it's a third party thing. Github launching it's self hosted enterprise is

You are right, a lot of companies would walk away from that pretty quickly as long as it's a third party thing. Github launching it's self hosted enterprise is what really enabled it to reach the larger companies, as they tend not to trust their valuable data to exist outside of their control. Slack has said before that they're going to release a self hosted version at some point, so they have to know this is true. I think it makes sense for them to focus on the larger market (personal use and the SMB sector) for now though, even though the enterprise market will really make them money, because it's a much lower pressure space where they can afford to experiment.