Well, my 4 gamer friends and I have quit WoW after playing almost non-stop since the original game's beta. By 'non-stop' I obviously mean that we've had active subscriptions and have played together at least 2-3 times a week since then.What finally made us quit? Glad you asked...

Prior to the Lich King, we worked hard to get to where we could run the Burning Crusade's Heroics. They were tough - we had to run arenas (badly, usually), lots of battlegrounds and lots of instances to get the gear together to run them. When we were first able to finish that first heroic, it was a time of celebration - we felt like we had accomplished something. We kept running them until we had all the gear we needed and wanted out of them. When WotLK came out, we rushed to 80 hoping for that same experience running those heroics but that's not what we found. Instead of a challenge we found super-easy instances with totally inadequate loot. We found that you could easily get enough badges to get the 'badge gear' you wanted and that there was really not very much of that either. Unfortunately, we don't really know enough people to get into the 10- and 25-man instances unless we want to run PUGs which we REALLY don't want to do. That left us with nothing to do but level another character. That works for a little while until you realize that you have the same thing waiting for you at 80 - some easy heroics, some mediocre gear and nothing else to do.

I predict that this is the begining of the end for WoW. People are 'finishing' the game and there isn't anything left for them to do. Any new expansion is a long way off and the high-end players are already done with Ulduar. I'm not happy this is the case - the game has given me a lot of good times with my friends - I'm just afraid that is the way it is.