I thought this was pretty cool. When buying the game, you can play the shooter aspect without having to subscribe. If you opt in for the monthly fees, you get access to the persistent war; conquering land, building bases, controlling resources, all that stuff.
http://kotaku.com/5385996/global-agenda-two-ways-to-pay-two-ways-to-play
http://kotaku.com/5385996/global-agenda-two-ways-to-pay-two-ways-to-play