1B hours played. Think about your experience with a couple hundred hours, and then multiply that by a few million similar instances - how much productivity has been lost? Or how much history has been learned, friendships built, and strategy developed? Similarly, how many billions of hours have been spent browsing Facebook, for better or worse?

I think one of the most important ethical questions we can ask ourselves is how can we write great gaming, working, and social networking software that has a net positive effect on the world through the hours that are spent in it.