Eurogamer published an article that provides a detailed look into Destiny's online and social components. Harold Ryan, president of Bungie, has some interesting things to say about what makes Destiny different from an MMO and the technology and ideas powering Destiny's connected experience. This is certainly worth the read especially if you still aren't quite sure what to make of Bungie's new world.
The second technology is an intriguing concept mooted by Ryan, one which I've never heard spoken of before: "social matchmaking". This will be the glue that binds Bungie's game servers to all those locally simulated solo or co-op games running out in the wild. In the process it will turn many thousands of tiny shards into the impression of a single persistent universe - one so big it could, potentially, dwarf Eve Online's New Eden.