I have a few friends with Substack newsletters. Mostly writers trying to find a way to make a living as the rest of their various industries collapse. They're mostly not in this little bubble - where substack's Nazi / underpant gnomes problems are well understood. They're mostly just pleased that substack makes newsletters easy and there appears to be a well-paved path to making some money.
Personally, I suspect they're going to end up in trouble. It will inevitably fall apart and they'll have built another house on sand. But this can be a hard case to make, there's nothing as comfy-looking as a port in a storm. And I don't want to lecture anyone, it's very hard to be on the internet without compromise. Maybe we should all have shamerolls below our blogrolls. Mine wouldn't be pretty.
But, in case it's useful, I'm going to keep this post as a place to collect evidence/arguments.
AMC: Substack did not see that coming (Thanks Phil)
Anil Dash: Don't call it a substack (Thanks again Phil)
And, the clue is in the URL leavesubstsack (Thanks Tom)