My immediate response to that is partially fueled by the ridiculous amount of trouble I've had with my internet lately. I hope that my problems are over for the time being, but while it was out my gaming options were definitely limited. Some games I couldn't play. Others I could, but the online component is the main draw. Still others, the game is single player, but (and this is silly I know) I didn't want to make progress in the game because I possibly wouldn't be credited with achievements.
But I still had a decent library of games that I could play, without any such worry or concern. If this trend continues to the point of being totally integrated into the mindset of developers, how many games, new games, will be out there to tide us over while our ISP sends out the repair guy, or when we move and are waiting for the internet to even be connected in the first place. Or while we are sitting in an airport with a laptop but no wi-fi waiting for our flight? How long before the old games we have from back before "online-only" are just a little too old, whether from graphics disillusionment or just already having played them enough that there's no surprises left, and we wind up spending our time doing something else? (Don't get me wrong, such a break from gaming here and there to go outside or read a book is a good thing to do regularly, even if infrequently, but I don't appreciate it when it's not on my terms.)
I haven't played the Diablo series yet, but I've been looking into trying out Diablo 2 to see if 3 would be something I'd like to pick up, seeing as I love the other Blizzard games. In the long run this probably won't affect my decision (might delay it though, if I decide to get it anyway) but I am a bit disappointed.