That's what made me give up WoW myself a few months ago, after playing for about year and getting my sister hooked worse than me. I played rather leisurely until Blizzard added Achievements. My play style changed drastically afterwards, especially with regards to holiday events. My desire to get titles (especially the Loremaster one) really burned me out. Brewfest was the final straw, since you have to do several annoying grind quests every stinking day for the two week duration. Really ruined the game for me. (Blizz had to extend the holiday for a few days even due to glitches that really screwed up the acquisition curve.)

I pity the players having to deal with the Valentine's Day event coming soon; that was the second worst, IMHO.