The Economist recently had a story about Google digitizing books. The author expressed his opinion that not all sorts of books were equally suited to being read in a digital form. Some printed books have content which is essentially "random access", meaning it consists of discrete bits, and you are equally likely to want to access any of these bits. You look up a word in a dictionary, a recipe in a cookbook, or a specific chapter on what you want to know about in a textbook. You don't read that dictionary or cookbook from cover to cover. Thus a digital dictionary or cookbook, with a search engine to find what you want, makes sense. A digital novel with a search engine makes a lot less sense. You probably don't want to read just the passage where Bilbo meets Gollum and finds the One Ring, you want to read the whole The Hobbit from start to end. A novel is sequential, not random access. And as you want to read all of it, having the book in printed form, so you can read it in a deckchair next to the pool, or whereever you want, is more practical than a digital version on a PC screen.
Now I was thinking that games too can be either random access or sequential. I recently bought Final Fantasy XII, but haven't had the time to start it yet. That is because I know that Final Fantasy RPGs are sequential, they tell a long story, and thus you better play them when you have time to actually get to the end of the story, which can be 60+ hours. A MMORPG like World of Warcraft is a lot more like random access. There is no story from start to finish, there are discreet little bits of stories in the form of quests. You can log on, look into your quest journal, choose any one of the up to 25 quests in your quest log, and do it. You can't really do content that is much higher in level than you, and doing content that is much lower usually isn't profitable. But in a certain level range of content there is no sequence, it doesn't matter what quest or zone you do first.
A MMORPG being random access is a huge advantage, because it gives you a wider range of possibilities to play with other people. As long as you are in the same level range as the person you want to play with, you can quest together or visit a dungeon together. You don't have to be at the same point in the story, because there is no story. On the downside the lack of story is a disadvantage for MMORPGs, because logging on for an hour just to grind some primals or gather some herbs for your next raid feels more like work than like a part of an epic adventure.
So I was wondering whether MMORPGs should have a main story line, a main quest line. Of course still with lots of side-quests and the freedom to do anything you want, even if you just log on for a short bit. But having a main thread to follow, besides leveling up from level 1 to 70, might give you more of a sense of purpose. Otherwise playing a MMORPG feels like reading a cookbook.