From Indie Game: The Movie:

The one major thing that made this possible is the rise of digital distribution. It used to be that retailers had a lot of power over every game creation company because that was the only avenue available to sell games and so nobody was willing to start distributing games digitally because Walmart would get upset at them and they wouldn’t take their products off the shelf and nothing would happen. But Valve changed that when they came up with Steam. They had no loyalties to retail and so they just did it. And then everybody said well, we have to compete with them, and there was this whole flood of XBox Live Arcade, Playstation Network and Wii Ware and it followed suit after that.

We’re seeing the same pattern with app stores on mobile phones or desktop, as well as digital books and movies. Digital distribution means that there are no gate keepers now, everyone is free to create and distribute what they want. If you create something people really want, you can become rich. It’s such an exciting time to live in if you’re a creator. It can be very stressful at the same time if you can’t execute. The pressure is on, you are fully responsible for your future.