Every other week, we examine the most popular Facebook games (according to monthly active users), looking at the top titles and developers on the social network to see Old School RS Gold who's attracting or losing players.]Though many of most popular games continued to lose no small number of users this past week, those losses aren't nearly as dramatic as the negative trends we've seen in the months following Facebook's changes to its application notification system, which cut "app spam" but limited the viral nature of many titles.For example, Zynga's FarmVille, still the #1 app on Facebook with 63.8 million players, lost almost 1.4 million users in the past two weeks, which is more than most social games have for their total audience. This time last month, though, the farming simulator surrendered almost 9 million users.The studio's Texas Holdem Poker at #2 fared better, giving up around 125,000 users for a total of 28.5 million virtual poker players. RockYou's non-game Birthday Cards, which was at #3 just two weeks ago, dropped to #8 as it bid farewell to 5.6 million birthday celebrators.Taking Birthday Cards' place at #3 is Zynga's Treasure Isle, as it managed to climb up a spot despite losing 1.2 million users, now at a total of 20.3 million. Zynga also took the fourth spot on the chart with Cafe World, which only lost 463,221 patrons and has a total of 20.2 million players.At #5, Mindjolt Games, a portal for more than a thousand casual games, lost 1.3 million players and has a total of 18.1 million. Mafia Wars by Zynga comes in at #6, less 760,165 mobsters (perhaps sleeping with FishVille's fishes), Runescape Account its total audience down to 18.1 million users.Zynga's FrontierVille, which has seen explosive growth since its launch last month, shot up ten spots to #7 after attracting 7.4 million new players in just the past two weeks, as the pioneering simulator now boasts a total user count of 16.8 million.