I have a sort of love/hate relationship with Dragons of Atlantis. It's the first Facebook game I've played for more than a month, and the first I've really been tempted to spend money on (though I've resisted). And there are things about the design that I really admire, but also things I hate. I've even fantasized about going to work for Kabam, to teach them some basic truths about wargame design that they apparently lack.
It's a Travian-style game, but with better graphics, and, at least for me, a more interesting backdrop. You start with a single city, and build buildings that produce resources -- good, stone, wood, and metal -- that you use to build more buildings and troops -- as well as other buildings that improve your tech or increase your troop production capabilities. The basic algorithm is a triangular/doubling one; each upgrade of a building increases its production as a triangular number, but building time for the structure doubles. (Google triangular number if you don't know what I'm talking about here.) This is minimalist, interesting design, and a fundamentally sound approach.