What was the secret of Blizzard’s success?

Most of the other MMORPGs (Everquest etc) require group play and rely on the hassle of scheduling play time together. – Paul Sams

And how do they plan to sustain that now?

World of Warcraft supports a lot of solo play. However, we want dungeons to be a group experience. In fact, we think the game is more fun overall when you play with friends, which is why we put so much effort into encouraging players to join guilds for Cataclysm. – Ghostcrawler

I realize that I may be oversimplifying just a bit. But I do find it odd that I can queue for any dungeon from 1-80 and can get in within 15 minutes or so. But any Cataclysm instance is an interminable wait … apparently, by design.