Let's imagine a hypothetical situation here. You're a new player and have been blind invited to join a guild. You, with hundreds of other newbies, help build the guild renown faster than most other guilds. Months later, the guild finally reaches level 100. Your reward for all this work? Being dismissed from the guild with 95% of the other "newbies" after having done most of the heavy lifting getting to level 100. Think this isn't going to happen? It is probably the secret game plan of some of these guilds. It will make a lot of the involved players very angry, perhaps even to the point where they quit the game. I have two possible ways to prevent this from happening (or at least punishing the guild for doing it)
1) The easy but quite fair way: Your guild has 1000 players. A player leaves or is booted and you lose 1/1000 of your renown. Another leaves or is booted and you lose 1/999 of your renown. Boot most of your guild and you'll lose most of your renown.
2) The hard but more fair way: Keep track of how much renown each toon earns for a guild. If the player leaves or is kicked, the renown is subtracted from the guild. This is the more fair way because it hurts the guild only as much as that toon has contributed to the renown. This is the hard way because it will require some bookkeeping code to be created to keep track of how much renown each toon earns.
This will also help make it so that guilds have to treat their members better because if they don't keep them happy, they can leave and hurt the guild's renown.
Let me know what you think.