[ProblemFactory]

ghshephard gave a good answer to the question "why do many people consider in-app purchases evil".

However, there is no doubt that "evil" approaches are more profitable than the doing the right thing.

Techniques such as the ones described in http://www.gamasutra.com/blogs/RaminShokrizade/20130626/1949... are very effective, and developers who do use them are likely to make more money. But that doesn't mean that any means necessary to make it into the top 10 grossing apps list must be considered ethical.