The main question is: why should anyone decline an update? Having an option is OK, but tell me a good reason why you want less bugs or outdated graphics? Lets take not the rare case into account whereas mods don't work, I can understand that argument, lets talk about an original game that isn't modified by the user, like on a console...
Automatic/Forced updates are a bad thing if the developer decides to change the game play in multiplayer games like Diablo II if the game forum is already flooded with postings about bad game balance because of that patch.
Or things like: that game does not like my graphic card with patch 10.02
