Have a look-see at Brody's latest article, called "Persistence of Action and Space." Here's an excerpt:

In some MUDs, 24 hours a day, I can walk through the city of Midgaard and encounter the brutish city guards who keep order. If I do something wrong, they're around to beat the snot out of me, until such time as I exceed them in strength and I get the chance to return the favor and snatch their armor and weapons.

You can read the article .