We are talking about platforms where the ads themselves caused users to leave. This is not what happened with Tumblr and it is not a good faith view to say so.
I only see you attempting to constrain the topic that far, rather than just the ways that advertising based models in general can pervert a company's incentives by turning away their core user base. Sometimes it's just changing the UX until your userbase no longer wants to show up. Sometimes it's literally just banning a huge chunk of your userbase for some reason.
