Does Tumblr have to be an app for any non-marketing reason?
If your website allows upload of porn, let it live in on the free internet as long as we still have it and don't waste resources on making it an "app". Problem solved. If that eats into your returns in a significant way, you don't have a viable business model.
> If that eats into your returns in a significant way, you don't have a viable business model
A viable business model is one where, by definition, consumers will purchase your thing at levels that are sustainable. People use apps more than they use web browsers for the most part. Tumblr has to build what people want.
If your website allows upload of porn, let it live in on the free internet as long as we still have it and don't waste resources on making it an "app". Problem solved. If that eats into your returns in a significant way, you don't have a viable business model.