You can change this now in User CP.
Guild Advancement, or Leveling, is a new feature that will be released with Cataclysm that will allow guilds to level up similar to a character. There will be a total of 25 levels, each leveling unlocking new perks, rewards, and such. To progress through these levels, members will contribute to leveling by completing standard parts of the game such as quests, dungeons, battlegrounds, etc. For each boss killed, quest completed, battleground won, experience will go towards the progress of a guild. By participating in guild groups, which are groups where 75% or more of the group consists of guildies, players will earn reputation with the guild which will allow them to purchase rewards such as guild heirlooms and mounts.
learn more here
the picture is a bit big but it shows all the talents
im wondering how some of the abilities will work though, will everyone be able to summon the raid?