Facebook's iPhone app, one of the most-downloaded of all time, and one of the first that many people download, is an interesting proxy for Apple's iPhone and iPod touch sales. And as expected, there was a big Christmas bump again this year.
Facebook's iPhone app currently has 57.3 million "monthly active users," meaning the number of people who have used the app in the last month. That's up 1.6 million since the morning of Dec. 24, when we checked and it had 55.7 million monthly active users. (It's been in the top 10 free apps for the last several days, and is currently #2.)
All Facebook has a nice interactive chart showing monthly active user growth for Facebook's iPhone app during December. As you can see, there has been a clear acceleration near Christmas. And it shows that Facebook for iPhone has gained 4.6 million monthly active users since Nov. 27, or 9% growth.
How does Facebook's iPhone app compare to some of its other mobile apps?
Facebook for Android has 20.9 million monthly active users, more than one-third of the iPhone app's user base. Its Christmas spike was smaller than Apple's -- up 900,000 monthly active uniques since Dec. 24, according to All Facebook. But it's up 4.3 million from Nov. 27, representing amazing 26% growth. Measured by units, that's a monthly activation rate that is near Apple's, without even having the equivalent of an iPod touch in the Android product lineup. (Though it may include some Galaxy Tab tablet users, while there's no Facebook app for the iPad yet.)
Facebook for BlackBerry has 26.9 million monthly active users, up 1.9 million from 25 million on Nov. 27, according to All Facebook. That's roughly 8% growth. (All Facebook's app stats seem to have stopped tracking this app after Dec. 21, so we can't see an apples-to-apples Christmas spike.)
But the king of them all, Zynga's new CityVille game, has 69.9 million monthly active users, up from 0 at the beginning of the month, which means it has added roughly 7 times the number of users during the month as Apple, Android, and BlackBerry combined.
Don't miss: The First 25 iPhone Apps You Must Download
On February 28, Axel Springer, Business Insider's parent company, joined 31 other media groups and filed a $2.3 billion suit against Google in Dutch court, alleging losses suffered due to the company's advertising practices.
