A business model that does not exploit users, ever. If you make it one where loss of trust leads to immediate loss of revenue and forces you to take the user side on all matters, well then all features are there to improve and maintain trust.
If it's free, you are the product. Not saying it's not possible, it's just unlikely to happen, unfortunately.
But open source thrives, is free, and we are not the product.
In theory redirecting ads money towards users, could be a path, in practice it seems the economic value is not there.