Nari - I've been in *alot* of guilds that are basically centered around a handful of 70s (who each generally have two or three 70s), and they run the place. All good. But, in alot of cases, they really have little respect for anyone that isn't right up there with them, and on some rare instances, they actually get mad at lower level characters who speak in guild chat, ask questions, or see if they can get some help. Other guilds will kick you if you go a week and don't come online.
Well, when we got back into WoW, all of us that started the guild were basically starting fresh - and we didn't want to be lvl 20 and have our guild 'run' by a bunch of 70s that we didn't even know. We decided to keep the guild recruits within 5 levels of our 'core' group of founders. Now don't get that wrong - once you've joined, you can race up to lvl 70 in a week, and you'll never be removed - we just don't want people at that level already to be added. We want to grow together - foster some team spirit, and the trust, friendship and cameraderie that comes from going through all that together - as a team.
Having a 70 do a run with you in one thing - and you're grateful, you got through that dungeon/completed that tough quest, etc. All good! But it's a totally different feeling than the one you have when you consider another character, this one being someone that advanced 40 levels with you, fighting, dieing, helping you advance, getting together for tough quests, etc.
It's that brotherhood/sisterhood feeling that we're trying to foster.