I think that what really sparked off gamers was the timing of their announcement. You don't announce the sequel until at least 2 months after the first was released. What happened was that most l4d players were already finding bugs and incomplete areas of the game, and then they were given the idea that valve was going to leave them in the un-finished beta-sludge until they buy l4d2. With valve's already high standard with tf2, they had just created a community of pansies and then slightly ticked them off. I mean, look at the whole hat saga. In WoW you don't get what you're looking for easily. Between the retard-checks and ninja-looters, many WoW players wait years to get what they wanted. Valve followers are spoiled, and take genius for granted.
...and WoW has systematically destroyed lives with its time consuming grind fests, "the more you play the better you are" gameplay mechanics. People have lost jobs and ruined their education and/or relationships by playing that game. I've witnessed it first hand with both of my younger brothers. One was an A* student due to go to Cambridge (The most prestigious University in the UK) to do a Chemistry degree, then he got hooked on WoW and got rejected last minute when his grades took a plumit. The other has just been kicked out of College. WoW has even been indirectly linked to 2 deaths.
I would hardly say that Valve made a bad move by making things reasonably achievable for this very reason. I certainly wouldn't go as far as to call them spoiled. It's like justifying poverty as a decent standard of living because people still manage to somehow exist that low. Those guys have as much right to protest their horrific living conditions as much as the boycotters have a right to protest the release of L4D2 and the mis-marketed support of its predecessor.