A really great diary-like article
in The Observer by Tim Adams last Sunday about one journalist's experience in the virtual world Second Life has an excellent explanation of the success of this metaverse (applicable to all metaverses, really):
The simple genius of Second Life is that it combines elements of Big Brother culture with the spirit of eBay. It plays to the contemporary urge to project ourselves into every story, to write our own emotions larger than anyone else's, to perform rather than to listen, to blog rather than read. And it also offers unlimited opportunities to shop.