I think too many people are getting the wrong idea from the headline.
It's not like the story is mandatory anyway. The reason why Elder Scrolls is popular is because you can forsake the story-line and explore the world. There will be nothing stopping players from doing that.
So certain parts of the game will be single-player. What's the big deal? If anything, it streamlines the story and allows players quicker access to the main quests. Once that is over and done with, you can focus more on the endgame.John Funk said:"The last thing you want to do is to have the final confrontation with Mehrunes Dagon as he's stomping across the Imperial City, and you see 15 guys behind you waiting to kill him because they're on the same quest." The TES Online designers were hoping to hit that feeling of "You're awesome, you're the hero" through technology, letting players confront the games' major villains in instanced areas by themselves (or, presumably, with friends).
It's not like the story is mandatory anyway. The reason why Elder Scrolls is popular is because you can forsake the story-line and explore the world. There will be nothing stopping players from doing that.