Madcat75 said:
1) It got boring
2) Too many idiots
I was in a guild simply because of friends of mine. Now, about 7 of the members had any semblance of basic intelligence (Staying OUT of the fire being a big part of Cata, don't ask me how no one seems to know that). And 7 good people can't carry another 3 or 18 morons through raids. I know, we tried.
I've actually quit multiple times, but I don't think I will be going back any time soon.
1st was same as this one, we had a solid 10-15 people, but we always had to fill the remaining slots with ANYONE (We didn't clear Naxx until our people had the gear from Flame Leviathan.)
2nd Quit after Ulduar, came back cause my friend needed someone to RaF him, so he had me make a new account. Ended up returning to the same guild (they now had about 20 people who knew how to play), played until ICC came out, and 75% of our good raiders quit, or joined other guilds. I quit again, since we couldn't kill Marrowgar
3rd quit, my friend who had me RaF with him, got into a guild that was clearing "Heroic" Lich King (which was a lie, he's just an idiot), I stayed until I got Shadowmourne, and quit until Cata came out. I was in such a good guild that even the Heroic versions of the encounters were one shot. It basically so boring since we started carrying peoples fresh 80's through, just for the extra challenge. We had the #2 Frost DK in the world (at the time) in our guild he pulled about 27k DPS on EVERY fight. I think our guild average DPS in a 25 man was over 200000.
I don't remember too well, was shortly after the Lich King fight was released.
4th and final time: Switched servers to play with my friends (again), Read the first paragraph.