9. Downloadable Content (DLC)
Of course, as wtih every reason I state in the article, this is arguable and subject to opinion. While not an absolute deciding factor of gaming becoming too easy, I think DLC is a culprit to look for a lot of the times. Developer X made game Y, and wants the player to buy post-launch DLC that continues the story, or is placed between the start and finish of it, or anything in between. How, then, will it be more luring for the consumer? "Maybe if the game is difficult and the player craves for more!", I hear you saying. Hell no (although sometimes that's reality, example, Artorias of the Abyss for Dark Souls). An easier way would be to make a good-but-easy game, let the player see it to the end without too much effort, and later throw in some DLC to keep them on your rails. Now, how much DLC would you buy for a game you enjoyed but finished after a long time of trying and sweating over it, and how much DLC for a game you enjoyed, but breezed through? With casual players in mind, I think the second option is more viable for developers.
Example: Resident Evil: Operation Raccoon City (imbalanced downloadable weapons)