First of all I would like to point out this game is amazing, very well done, and generally a blast to play. I think Valve did do an excellent job in the development of this game. But I would like to point out an event that happened last year. Last year, in December I believe, Valve decided to make the game a free download for a day. Now, this wasn't like the "Free Weekend" events in which they make a certain game free for just a weekend and when that weekend ends you can't play the game. Oh no, this was not that. Instead, they decided to make the game free to download that day, and when you downloaded you could keep the game for yourself. I myself actually picked up the game when this happened, but to be honest, now I feel awfully guilty. First things first, the event was practically hidden from everyone. If for some reason you decided to have a look at the Left 4 Dead 2 store page that day, you would realize that it was free to download, but it wasn't like a big annoucment type thing in which in the front page they put a giant picture saying "LEFT 4 DEAD 2 IS FREEEEEEEE", oh no, it was very well hid in fact. Actually the reason that day I found out about that was because PC Gamer had made an article about it and I checked it out. Now, I would see why Valve didn't advertise it because if they did, about every single user on Steam would have found out and everyone would own the game which would mean they would get less money from Left 4 Dead 2 after that because the only people which would buy it would be newcomers, and that means less money for Valve, but still, it was kind of a ♥♥♥♥♥ move for the people that were waiting for a sale for it and they didn't get informed about anything. The second thing is, many people were downloading it, including me, and that sadly meant that Valve was welcoming a bunch of noobs to a gaming community full of people that really, really take the game serious. Not a very nice thing for people that bought the game, let's say, the day before the game became briefly free.
Sorry for this big blob of text, it was just my personal opinion and I felt like this had to be said.