There is a trend to mobile apps toward single purpose apps. This is one result of a study by Nielsen, which lists the top 10 mobile apps of 2013. The study is related to the US market, but should be relevant to other markets as well as the popularity of messaging and chat apps is well known.
Concretely the big players are confronted with a decrease of the use of their mobile apps. This concerns all big players, Facebook, Google and Yahoo as well as the Ask Search Network and what wonders the most even YouTube. The fastest growing single purpose app has been Instagram and Twitter, which is an exception, as well had a good performance. Typical growth scopes are social networking apps of different, the mentioned Instagram with its photo and video sharing facilities as well as chat and messaging apps.
Another study by the way referred to the difficulties of the market with less than 1% of app creators being able to earn money with their apps. The data of the Nielsen study are summarized within an article by MediaPost and available by a Nielsen press release.