This Week’s List of Fastest-Growing Facebook Apps by MAU Shows Unusual Gains for Some Apps

[Update: Facebook has responded to let us know that the below stats are due to a bug in their reporting, which they’re currently working on fixing.]

Our Monday list of fastest-gaining Facebook apps by monthly active users is more than a bit out of the ordinary this morning. We’re seeing huge growth for several apps over the weekend, in a pattern that looks very similar between each affected app.

Regular readers may recall that the same thing happened in mid-June; it turned out that Facebook had made an internal change to show the previously unknown, but accurate stats for a number of apps like Quiz Planet! and Facebook for Android. Has the same thing happened again? We’re not sure yet, but if so it’s big news for developers.

Take a look at the AppData top 20:

Top Gainers This Week
Name MAU Gain Gain,%
1.Original Café World35,324,196+15,100,354+75%
2.Original Texas HoldEm Poker41,597,080+13,612,033+49%
3.Original Mafia Wars Game24,142,623+6,429,541+36%
4.Original Zoo World12,857,340+6,053,805+89%
5.Original PetVille17,823,978+3,861,130+28%
6.Original Birthday Calendar7,662,413+3,761,963+96%
7.Original FrontierVille24,984,631+3,598,109+17%
8.Original Windows Live Messenger6,138,142+2,666,076+77%
9.Original Restaurant City13,017,032+2,289,626+21%
10.Original Phrases23,693,492+2,194,455+10%
11.Original Happy Island8,681,928+2,044,392+31%
12.Original Sorority Life4,978,879+1,750,713+54%
13.App_2_125301840827866_9721 Market Street1,828,168+1,674,500+1,090%
14.Original Hallmark Social Calendar2,154,008+1,480,988+220%
15.Original Drinks for All!2,131,663+1,463,687+219%
16.Original Friends For Sale!3,377,538+1,402,706+71%
17.Original Circle of Moms2,592,284+1,210,558+88%
18.Original Who thinks of you?1,176,603+1,050,504+833%
19.Original Zoosk6,318,780+989,944+19%
20.Original QuizBone3,350,837+927,701+38%

The top three apps on the list show a combined gain of about 35 million MAU. As it happens, they’re all Zynga games. That company shows a gain of almost 50 million MAU over the weekend.

Prior to today, it was widely-accepted fact that Zynga had lost about 50 million MAU since April. While it’s possible that Facebook is experiencing a bug in reporting — we’re still trying to get responses from both Facebook and Zynga — it also seems possible, given the latest data, that Zynga never lost ground at all. We’ll be following up on that story over at Inside Social Games.

But the gains aren’t limited to games. Windows Live Messenger, Hallmark Social Calendar, Friends For Sale!, Circle of Moms and Zoosk all show a pretty much identical kick in growth over the weekend to the games at the top of the list. Here’s a representative example:

We’ll post an update when we know more about what’s happening.