One way to compare how different mobile platforms are doing is to look at the usage numbers from a popular app. Facebook reports their usage numbers alongside other apps (see here here here & here).  I went and graphed the usage figures a few weeks ago and present them below [no guarantee they're 100% up-to-date...in fact it looks like the Android and Palm figures that Facebook lists have changed drastically since the time I originally started writing this post]:

Wow.  It’s easy to see that the Facebook app usage on the iPhone platform trumps all the others.  From what I’ve gathered talking to other cross-platform mobile developers, these results are generally in line (at least for free applications):  Blackberry generally has half the install base of iPhone, and Android and all the others continue to lag far behind. Let’s look at another free app: Foursquare, which shared their platform breakdown via a tweet.

Android has an impressive showing, which could make sense given the application’s early adoption by techie types. Unlike Facebook, it hasn’t (yet) gained mainstream adoption. The differences across platforms become even more stark when we focus on paid apps. Here’s what the breakdown looks like for Exit Strategy NYC:

Exit Strategy NYC launched across all the platforms on the same day.  As you can see, nothing holds a candle to the Apple platform. What’s especially interesting is how poor the sales are for Android despite all the hype and press it gets.  And it looks like we’re not the only ones who have been disappointed: Gameloft (a mobile game company) announced in November they’re going to focus less on Android because they’ve sold “400 times more games on iPhone than on Android.” And Larva Labs discusses “The well known game Trism, which sold over $250,000 in it’s first two months on the iPhone. On Android it has sold, to date, less than 500 copies. That’s $1,046 total earnings, max.” How can we explain the massive difference?  Lots of ways: different market sizes, different app store user experiences, different user expectations.  In fact, I could probably write a book on the subject (Pssst, O’Reilly: my contact info is along the right sidebar…). But instead, I’ll try to focus on what I think are the main drivers:

• Apple’s app-focused marketing. Apple’s marketing focused strongly on apps. People buy the devices with the intention to purchase lots of apps! In fact, the average user has downloaded about 50 apps (over 4 billion apps have been downloaded and 85 million devices have been sold). Wowza!
• Lack of an Android Touch. The iPod touch nearly doubles the amount of devices with access to the app store (from 50M to over 85M).  No equivalent device exists on Blackberry or Android. There simply aren’t that many Android devices yet.
• Lack of awareness among BlackBerry users. Most Blackberry users don’t know they can download apps.  (I’ll go out on a limb here and say that Facebook has done a great deal to help, but awareness is still lagging.)
• Poor penetration of Blackberry App World. Blackberry is a late comer to the app store game.  Blackberry App World only launched a year ago in April 2009. Blackberry App World doesn’t come preinstalled on new Blackberry phones! Users have to manually install the software to access the store.  This is ridiculous.
• Blackberry’s App World’s bias away from paid apps. Blackberry doesn’t make you setup a payment method to access App World or download free apps. This creates a roadblock for paid apps and creates a huge bias towards free applications.  Paid apps require Paypal which many users hate.
• Poor Android app store experience. Best explained here.  And for paid apps, Google checkout is required which hasn’t really hit widespread adoption.  So it’s not surprising that Admob reports 63% more app purchases for each iPhone user vs Android users (1.8 vs 1.1 monthly paid apps).  Even most Googlers can’t purchase paid apps because of weird restrictions on their employee unlocked handsets.

So those you have it — a few potential reasons for the differences.  At the end of the day I believe small developers are best advised to put their energy into developing for the Apple platform. Building products for the other platforms probably doesn’t make sense at present time unless you have a game-changing mobile vision for a product that’ll take years to complete and needs the openness that Android provides.  Or if you’re a startup showing traction that relies on a strong network effect to take over the world (ie Foursquare). Or if you’re a big company with tons of cash to build out your branded app — like Facebook, which tries to have versions available for every phone possible!  But gosh, I’d hate to be that engineer locked in a basement building for all six users of the Sony q7d3m1p$9!&9b7u64gph model phone.