Comment by FooBarWidget

Yes it's a single point of failure, but so what? I don't particularly care whether other organizations fail at the same time as I do, I just care whether I fail. Hosting my own chat system does not solve that problem. In fact, it may make it worse because then I have to worry about system administration, and Slack probably has more expertise on that. It's likely that they can fix this problem for all customers faster than I can fix my problem for myself. And it's not like I'm crippled when Slack is down. If it's urgent I can use the phone, and my todo list is stored outside Slack.