I can understand Facebook and Instagram, they can make money by using strong network effects. It's essentially the same thing Microsoft did, monetize a common p

I can understand Facebook and Instagram, they can make money by using strong network effects. It's essentially the same thing Microsoft did, monetize a common platform and exploit the lock in effect. But Slack largely lacks that. A startup might setup a free Slack instance, then run into its limitations and pay for extra service. But aside from some institutional inertia, nothing stops a company from switching. You don't need Slack to reach your public, unlike say Facebook. It's a chat tool, an average one, and you can easily migrate out of it. As a repository for essential business knowledge, Slack is not a good solution and could even be harmful compared to things like a wiki or documents stored in a revision control system. And as a pure SaaS offering, there is no way in hell Slack is worth $7 billion. You can replicate its functionality for less than $100 million, and get native, fast apps. There must be something else, but I just don't see it.