Achievements can now be gained as a Guild in the upcoming Cataclysm expansion. They have given more motivation for guilds to progress and conquer goals together. Every guild member will have their role to play in leveling their respective guild and unlocking achievements.

Guilds can level up to Level 20 (not concrete yet though) which experience can be obtained via members leveling, reputation, BG wins, Arena wins, profession ranks and boss kills which requires 75% dungeon/raid member in the party or raid.

The whole idea to leveling your guild is to obtain Talent points for each level which can be spent on your Guild's talent tree. Each upgrade or points taken will effect every single Guild member such as cheaper repair costs which is very cool in my opinion.

Anyways take a look at the following video to learn more about the upcoming Guild leveling system and Guild talent tree: