We've talked about MMORPG's but not much about MMORTS's (that's Massive Multiplayer Online Real Time Strategy games. This means command from the air build your civilization type game.
Society (published by Stardock) seems to be the one that everyone is talking about right now.
Stardock say that it will be slow to build your empire (as slow as building a character in everquest or WOW). Subscription will be optional, but subscribing players will have in game advantages of non-subscribers.
Conquest will be part of the game, but not the main thrust, at least according to the site. They say they will start out with you solving a basic problem for an individual person in your empire, and then it gets more complex from there. (sounds almost like spore.)
There are a couple of other MMORTS names out there mankind, boundless planet, ballerium. All are in developement. As is the case with mmoRPG's it's mostly fantasy or sci-fi. Apparently the RTS is the only game that doesn't always choose fantasy or sci-fi settings.
Of course text/browser based games which are basically MMORTS's based in text have been around for a long time. Utopia has been around since 1999. A very addictive complex game that has 100,000 players on it. (At most 40k per server) Also very social, I felt more connected in that game than in any MMORPG, mainly because the game automatically groups you in a "kingdom," and you have to play politics within the kingdom and also with other kingdoms.