I understand that flying mounts are a convenience for players who have no patience for the environment of this game, and would rather instazoom to their mining/herb/arch nodes, or can't be bothered spending an extra five seconds reaching an NPC. But it has become apparent that letting flying become the norm for all of Azeroth has killed the sense of scale that was once so incredible in this game.
WoW has a beautiful art style, complimented by a huge draw distance that creates the feel of a large, comprehensive world that's completely open. One thing about WoW that's great is that nearly every environmental feature is accessible by the player. Now, some think flying seals that deal by letting you park your dragon on top of mountains and buildings you couldn't reach normally on ground. But while it's great that you have a freedom in accessing all parts of the game world, it kills the sense that the nature in the game is something immense and massive; what's the point of gigantic, imposing mountains, towering buildings and ziggurats, or vast oceans if you can just zoom on top or over them? Part of any atmosphere in a game is a sense that the player is smaller than the environment; when you can just instantly reach everything in the game, a sense of scale is destroyed. Plus, if you can just fly over ANYTHING in the game, there's no sense of a dynamic environment or any real danger in the game. World PvP is ruined.
Not to mention that flying mounts are inherently boring; flying in WoW is the exact same as swimming in the sky. I understand that the engine can't accommodate more visceral flying in, say, Aion, where you can glide and thrust rather than just fly in a complete straight line with an absurdly unrealistic ability of precision. If flying is really so big a convenience for players, I'd like to see Blizzard make attempts to have it be more fun--flying mounts are far more monotonous than ground mounts.
I know the common response would be to just stay on your ground mount and STFU. But the problem is that nobody else will do this, including enemy players; thus, social interaction and WoW's famous world PvP is going to be hindered because players are incentivized to hop onto their mounts and derp around in the sky. Random, spontaneous player interaction in the game world is killed, all for the sake of "convenience."
The bottom line is that I'd like to see flying mounts removed all together from Azeroth, and at least confine them to Outland or Northrend; they limit player interaction and reduce the sense of scale in WoW, two negative impacts that make this game less and less of a social MMO experience.