Those orgs compete or conflict, and this is the heart of the political posturing in MPGs. Very cool stuff. Occupations - this is a new one in graphical MPGs. It's what OSI has created by taking a stab at creating a real economy. I'm not sure how this will work out in the end once things are balanced, but it's definitely a challenge.
People get bored.
Some have the inclination to get involved in the other seven final challenges, and some don't. A lot of what determines if people stay with a game is how well the game supports the above 7 items. You just can't program an NPC to be smart enough, funny enough, aggressive enough, cool enough, unpredictable enough, etc. to hold a real person's attention for any length of time. Once that's over, if the game can't support and support WELL real staying-power playing that the 7 above give, then you might as well stick a fork in it, it's done. This is the final circle of game play.