Competitive Survival Multiplayer in Minecraft? Don't know how that would work... Other than taking over most the map and hoarding resources... But then again, the map can generate on and on and on far beyond what any player could ever get to really...
Notch has said that survival multiplayer isn't the be-all end-all gamemode. Some kind of adventure mode has been alluded to, and players of SMP have invented Spleef: http://www.minecraftwiki.net/wiki/Spleef