Why is this game online only?
Those of us to bought this game on the release date surely asked ourselves this question. It was impossible to login and play the game since the login servers where flooded.
But why would Blizzard want to force people online? The answer is pretty simple
By making a game dependent on online features it is hard to crack and create piracy copies. This will increase the number of games sold and also revenue, and such cover the cost of keeping servers up and running.
Blizzard wants you to download the latest patch updates to the game. By forcing you online, they also force you to upgrade your game in order to play. This is also a trick that makes it harder to piracy the game.
- Social aspects
By connecting to Facebook, Blizzard will make sure that you're constantly aware of your friends that are online playing. This makes the game last longer and keep people playing it.
The big downside of "online only" games, is that 12 years from now when Blizzard has released Diablo 4 and shutdown the servers for Diablo 3, this game is unplayable. So keep playing while you can, this game has certainly a future death date.