Brewfest

One of the things I do like about online games is their ability to be seasonal. Right now it's brewfest time in World of Warcraft, and they've set up some amusing little quests and visuals to add color to the game. It's not really something you could very easily do to a traditional game, and I think it's something that will be taken advantage of even more in the future. There are actually a lot of opportunities in this area - a game which is supposed to take place in a certain real-world location could tie in to local forecasts, for example.