I feel like your comparing apples and oranged when you get into a term as vague and vast as “virtual worlds”. At what point is something even considered comparable to its supposed competition? Is Second Life, a program that I’ve always considered more of a browser or tool than a game, even comparable to WoW? In function, form and purpose they’re entirely different.
Do xbox lives subs count as part of an mmo? Is Halo’s multiplayer a virtual world? Is an fps with traditional multiplayer but a tacked on auction house an mmo? Does persistence make something a virtual world? Does instancing not? Is it a virtual world when it has thousands of players or is it a “virtual world” when you have four people playing ninja turtles together online? They’re in a world, they’re socializing, and its online. How is that different than doing a dungeon run with your fiends in WoW or running a race with some buddies in facebook’s digipets online?
The truth is the term “mmo” has become more and more vague as of late. Most games these days have a strong multiplayer focus as well as a sense of online progression that would have been previously confined to this genre. To add to this confusion, a lot of mmo’s have pulled their complexity and “massiveness” back to the point where they more closely resemble a series of instanced scenarios than a sprawling seamless world populated with thousands of players simultaneously.
And now we’re fitting multiplayer flash games that run on social networks into this already ill-defined and somewhat imaginary digital phenomenon? If you ask me the term “virtual world” has become mute by this point and arguably, even the term “mmo”. We’re playing (and working) in an environment where every program and website is online and persistent; complete with its own span of socialization and change. The days when all we had were everquest, starcraft and goldeneye are long gone. It’s time to stop using such marketing terms to compare apples and oranges when we’re now faced with an entire supermarket of digital, ever-changing food.