There's a new group report out by Project Horseshoe (a small conference that addresses issues in game design) which lays out a guideline of "golden rules" designers should take into account when considering fair ways to request money from players.
The report aims to provide developers just beginning to work in the area of monetization a solid set of guidelines for approaching their work with ethical consideration. This could prove useful, as the industry has received criticism over poor monetization practices in the past.
Written by a group of industry professionals (including Joel Gonzales of Firaxis and Crystin Cox of ArenaNet), the document lays out a set of golden rules specific to game design which provide a framework for designers to evaluate specific designs and motivations for monetization strategies.
The report also analyzes common monetization strategies used in the industry today, and points out the ethical ramifications each strategy can have on the player. For example the report acknowledges that there's nothing inherently unethical about free to play games, but developers should be transparent about how they intend to make money from their players.
"Having a set of ethical guidelines is a good way to ensure that we are treating our players fairly as it allows for a predetermined quality bar to be set and measured against," the report states. "We can and should make games that adhere to ethical guidelines while still being profitable."
Make sure to check out the entire group report at Project Horseshoe.