https://www.youtube.com/watch?v=x6sSa5NpqUI
The lion-manager is gazing out a window, has a passing thought about "flying umbrellas". Naturally, he instantly sends a mass-broadcast, interrupting and disrupting the work of the entire office. (Who all, of course, leap joyously to implement his brilliant vision.)
Now, this makes a lot of sense if you want to sell copies of Slack, since it appeals to the managers with the power to approve-purchases and mandate-adoption... But it implies Slack is going to either become the latest tool-of-oppression at a dysfunctional company, or that managers are going to buy Slack with the idea that they can use it to micromanage everybody.
Further on, as the Slack team adds features, guess what kinds of features are going to get priority? The ones that sell. Which ones are those? The ones that lion-managers love and other-employees hate.