Cristina gives us more numbers on why mobile is so hard:

When I look at retention on mobile today, a 30% monthly active user rate is much higher than what publicly available data tells us:

Socialcam: In June, Socialcam had 83.6M monthly active users connected to Facebook. Today, it has 4.3M. This is a decrease of 95% in 5 months.

Viddy: In June, Viddy had 20.9M monthly active users connected to Facebook. Today, it has 660K. This a decrease of 97% in 5 months.

Draw Something: In April, Draw Something had 36.5M monthly active users connected to Facebook. Today, it has 9.1M. This is a decrease of 75% in 7 months. 

Path: In December, Path had 250K monthly active users connected to Facebook. Almost one year later, they have about 780K monthly active users. While the 2.0 version of their app led to much initial growth, it seems that growth hasn’t affected churn. 

Every company in mobile wishes they had the retention rate of Instagram - but very few even whisper the words “monthly active users” to the outside world.  An app is only a long-press away from being dismissed to the second, third or fourth page of apps on a user’s device. How mobile companies aim to defeat the retention problem in a world of fickle social users will be their true test.

Oh, btw, friend spamming doesn't work.

No wonder it's so hard to build a good base of active users on mobile.

Every major Internet service with the exception of Instagram has grown because of the Web, not because of mobile.

Exponential growth is usually followed by exponential decay.

Bribery, porn, and spam might help grow in the short-term but they hurt in the long term.

The real winners are SocialCam and DrawSomething/OMGpop who saw this well enough to get out while they were hot.

 Perhaps Path has good retention in Asia? 

Tough road ahead for Viddy....

I don't see how Viddy survives this.

And Path has 780k monthly active users WORLDWIDE. Ouch.

Correction: Path has 5 million downloads, 2.5 million monthly actives, 1.2 million daily actives.

Source: http://www.businessinsider.com/path-search-feature-2012-12

This is a great post. However, I'll add one bit of clarification. "Retention" on mobile is a problem, but it's a 2nd order problem. Of the 1st order is "Distribution." 

Semil, those are related problems since they both require engagement.

Distribution: are enough people engaged to download the app?

Retention: are enough people engaged to actually USE the app?