"Seventy-five percent of the titles on the market that claim to be 'MMO' are actually single-player or limited group-oriented games that just happen to have lots of other people running around, doing the same things and having no impact on one another. In my view, to truly be a 'massively multiplayer' experience, the extant population of the game world has to have some sort of impact on you – regardless of whether or not they're in your raid group or guild."

Completely agree. This is everything that's wrong with MMOs today.