The slack model of only paying for active users is so much better than paying for users that may not actually be using the product:<p>How users are counted towards billing?<p>"Once users are created they are automatically counted towards billing even if they don't accept the invite or ever login. A user must be explicitly deactivated, deleted, or removed from a synced user directory (if you have Google sync) to not count towards billing. Learn how to add or remove users."<p>With slack, they are strongly incentivized to keep the product engaging enough to hold onto users.