Operator storefronts and portals now account for just 6% of content downloads worldwide, with Google Play and Apple's App Store now comprising nearly 70% between them. The increasing popularity of OTT (Over The Top) stores had led to many operators closing their own mobile storefronts.
There may be a silver lining.  A report "Mobile Content Business Models: OTT&Operator Strategy&Forecasts 2013-2017" from Juniper says that by offering carrier billing to third-party storefronts, operators could more than offset the continued decline in portal revenues. According to the report, storefronts which have already integrated carrier billing solutions have seen a 5-6x increase in conversion rates compared with credit card billing, together with an uplift in average transaction values. 

 Revenues from mobile content, monetized through direct carrier billing, are expected to rise from $2 billion last year to more than $13 billion by 2017, according to the new report. The implementation of carrier billing allowed storefronts and developers to monetize unbanked/underbanked regions and demographics for the first time.  

 As report author Dr. Windsor Holden pointed out, "While many operators have now abandoned the own-brand storefront approach, by leveraging their billing relationship with the end user they can retain a foothold in the content play. Simply by offering consumers a billing choice, monetisation rates will rise dramatically." 

However, the report cautioned that carrier billing for higher value content would be less effective amongst prepaid users given the relatively low top-up levels in most markets.

 Also notable: Google has surpassed Apple in terms of app downloads on an ongoing basis, though monetization levels of Android apps are markedly lower. In-app billing and freemium has become the prevalent business model, but there is still a role for PPD (Pay Per Download).