As downloads declined in April, spending on marketing began to rise, Alder noted. "[W]e observed more aggressive advertising spending as marketers moved out of the first quarter lull and began to seek new opportunities to compete for rank especially in the dynamic social networking and games categories, which experienced volatility during the month," he said.

Heating up developers' interest in social networking apps was Facebook's eye-popping for a billion dollars, the Fiscus report noted.

"Additionally, a number of new gaming apps hit the market in April, driving fiercer competition in the popular games category and increased interest from the developer community at large," it added.

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