When did you start, and when did you quit?
Feel free to say why and stuff.
I personally started playing at Wrath of the Lich King on retail WoW. I loved this expansion and had a great time playing, both PvP and PvE.
I was still playing in the beginning of Cataclysm until they have released 4.1 patch. I remember I really didn't like one of the changes regarding PvP and felt like I have wasted time playing on Cata, and just quit. Also most of my friends stopped playing too and nothing kept me there. I kept reading about WoW from time to time and saw how cataclysm ruined WoW a bit. It was just the beginning though.
Mists of Pandaria expansion was on the way. I came back to WoW: MoP for literally 15 minutes, because the pandaren area just made me laugh, and so did the new 'talents'. And so friends kept telling me there are only few short dungeons, and the classes are really unbalanced. Until not long ago, I had no idea there was something like LFR and Flex, which just confirmed that MoP was just terrible.
As of today, I do plan to return for the new expansion and I really look forward to it and hope Blizzard won't ruin it even more, because I seriously miss old days of WoW.