>Here’s what companies don’t understand: if you promote your product through a loss leader — which is arguably how Slack became popular in the first place — changing your pricing at a later date will piss people off.

I'd argue that most companies understand that perfectly well. They have a generous free tier to drive growth. Once that growth is attained and demand starts to level off, it's time to trim the resources devoted to free and force users (to greater or lesser degrees) to either start paying or go use someone else. There's great wailing and gnashing of teeth for some period of time on HN, Twitter, etc. but life moves on.

It's a pretty predictable playbook. See also Heroku of late. It should probably also come as no surprise we're seeing a number of examples of this going on at the moment.