It's also a great example of a hype cycle - it was going to be the future, it was going to be everything, corporates had offices in there, universities had campuses, there were virtual music events and art galleries, there were real-dollar millionaires made from virtual real-estate.
When the hype died down and the smoke cleared, there were still people wanting to use it, but not that many, and not in the way we were all told to expect, and the corporates realised they didn't need a bank branch or an SL office full of virtual meeting rooms in there after all. Neat sandbox with interesting ongoing uses, not the new centre of all our online lives.