IGN has some interesting coverage of a panel at GDC 2008 that featured some of the top names in the MMO world who got together to discuss the future of the genre.
"On hand were Jack Emmert of Cryptic Studios, Mark Miller of NCSoft, Min Kim of Nexon and Rob Pardo of Blizzard Entertainment. MMO newbie Ray Muzyka was also on hand to share his thoughts as BioWare moves into the MMO arena. [...] The conversation got a lot more heated when the subject of micro-transactions was introduced. This is a popular revenue model in Asia, where the games themselves are free to play but charge a premium for a variety of premium extras, from vanity items to additional content or abilities. It's a model that's working well for Korean developer Nexon but hasn't been adopted by many American developers."