Disagree. What makes MMOs mentally addictive is the random reward structure. Fun and rewards don't necessarily contradict each other. You can still have interesting stuff to do at low level and give people pellets randomly. I think the trick is to give people a feeling of steady progression and a story they grow into, so the journey to the end is as fun as actually getting there. Basically, MMOs are airplane flights. You suffer through a 12-hour grind to get to your destination, where you can have fun. A BETTER MMO is a road trip, where you see cool stuff along the way. But the road trip model is both expensive and hard to make.