In some freemium games I'd say that the scaling of difficulty can be an ethics question. What if a free game promises free gameplay but actually requires hundreds of dollars of in-app-purchases to actually experience the core gameplay? There should at least be a gambling-industry level of ethics.

*Sure, it's not a big deal if the free player just loses some time trying the game out before dropping it, but what about the player who put in $20 thinking it would get them X, but it turns out that actually only got them 10% of the way to X?