There’s a concerning new trend taking place on the U.S. App Store which is impacting companies large and small: many apps are seeing their downloads decline, even as overall App Store revenue grows. The data, which comes from app intelligence firm Appfigures, suggests that some of the biggest apps on the market are slowly losing their appeal in the face of increased competition, pulling overall app installs down. This is not happening at a scale large enough to dethrone the big apps, however, the firm tells us. For instance, Facebook remains one of the most downloaded apps every month. But...