Here you go. This only includes topics which were credibly and sincerely called the ruination or death of WoW by enough posters that it was an ongoing issue. I'm not listing "I hate this about WoW" stuff, this is entirely "This will/has ruin(ed) the game" level stuff.
And I've left out any external sources. Other games that'll kill WoW like Aion, DDO, and Auto Assault, they're on another list.
Since it began, it's been ruined by rooftop camping, the removal of rooftop camping, the lack of honor, the implementation of honor, the lack of dishonor, the implementation of dishonor, the removal of dishonor, the removal of wall walking, rank rewards, decaying rank, the removal of rank decay, the removal of PVP titles, Ahn'Qiraj, Scourge Invasion, Zul'Gurub, the cost of mounts, the lack of information about TBC, all information released about TBC, playable Blood Elves, playable Draenei, Horde Paladins, Alliance Shamans, flying mounts, the timing of the release of TBC, the cost of flight, Jewelcrafting, the LFG channel, holding people accountable to the Terms of Use, meeting stones, arenas, the number of arena teams one player can have, arena-based gear rewards, the lack of battlegrounds, the addition of battlegrounds, everything about battlegrounds, Illidan being killable, Daily quests, instance-based reputations, the Darkmoon Faire, /pizza, playable wisps, Tinfoil Hat, the Armory, Warden, the lack of information about Wrath, all information about Wrath, a failure to revamp old world areas, the inability to transfer from PVE to PVP servers, hero classes, siege engines, cold weather flying, Wintergrasp being a PVP zone, death knights, the inability to start a new character of any class at 55 or higher, the lack of a dance studio, character recustomization, the inability to change race or faction, the cost of mammoths and motorcycles, Spirit of Competition, the fall damage negation of mammoths and motorcycles, the removal of fall damage negation from mammoths and motorcycles, the ability to transfer from PVE to PVP servers, dual specs, Achievements, holiday events, Mountain Dew Game Fuel, streaming Blizzcon ’09 on pay per view, the revamping of Onyxia’s Lair, Worgen for the Alliance, Goblins for the Horde, revamped old world areas, the ability to change faction, the ability to change race, new race/class combinations, purchasable vanity pets, Icecrown Citadel, cross realm LFG, Celestial Steeds, the Disenchant option added to Need/Greed, combining raid lockouts, the initial announcement, then delay, then lack of information, then announcement, of the new X-53 Touring Rocket RAF reward mount, the removal of Path of the Titans, Archaeology, changes to Archaeology, the introduction of RealID as an option to the game servers, the introduction of RealID as a matter of mandatory disclosure for forum participation, as well as weekly maintenance and patches 1.1 through the current one inclusive.