I don't know, every year people keep shouting that one player games are dead. What GB Games says is a bit less silly, fortunately. He talks about adding in a feature to your single-player games that let the users share stories. Thus making a single player game with a community.
This segues into two things I'm interested in that are actually just one thing.
The first thing is that he's talking less about fundamental game design and more about viral marketing. While you have to be a bit careful in your game design so that you can allow this kind of sharing (and probably content swapping), the real idea here is not to change the way the game fundamentally works, but simply to change the way that the players relate to it and each other.
The other first thing is that I feel anything that affects the player's experience should count as part of the game design, even if it isn't actually much part of the game. Dwarf Fortress has a very strong community for its size, but there are no inherent tools to help you share your experience. The players share anyway, leading this to be part of the experience even when there are absolutely NO tools, no hint of anything to help you share, in the game itself. This is capitalized on because the sharers usually take a "Lets Play" approach and add in plenty of color and flavor that is also not in the original game.
These two first things combine into one thing: the idea that a game isn't really a standalone package any more. Whether your game contains the tools or not, the players will want to communicate and interact with each other.
Even, and here's the part a lot of people don't like, even just in one-player games.
I love one-player games. I don't much like multiplayer games and loathe massively multiplayer games. I buy more than half of the single-player RPGs and first-person-shooters that come out for the consoles I own, and quite a few for the computer as well. I am Mr. Single Player.
But I find one truth to be particularly glaring: the games I play longest are the ones that I visit on-line sites, download mods, look up cheats, and read silly things about. These places I visit are very rarely associated with the game devs. They are almost always fan-sites or faq-sites. Moreover, I don't think their existence causes me to play the game more. I think their existence is because people like me play the game more.
Dragon Age is a good example. Most Dragon-Age-related sites are either A) associated with the devs, B) sharing space with other games such as Oblivion, or C) dead. Dragon Age just doesn't have the same mindshare as, say, Oblivion or the Sims, which have literally thousands of indie sites dedicated to talking about them in niche terms. Despite the fact that these games have no inherent "sharing" technology.
Well, the Sims does have uploadable "family albums". Which are, as far as I can tell, less commonly used than simply posting to a foum. And on the other side of the spectrum, Spore is specifically designed around allowing players to share. And... it's not very good. No longevity at all.
What I'm trying to say is that making it possible for players to share stories is rarely a bad idea... but if you make a game that gives your players stories to share, there are plenty of already-made solutions for the sharing that they will happily use.