Facebook is to allow app developers to advertise their products on its members' mobile-device news feeds. Everybody knows that the Facebook shares have nearly dropped half their value very recently. Facebook had previously warned that’s its financial health would suffer if it could not find ways to make money out of its mobile users? So what happens now? It invites software developers to sign up to a "beta" test in which they can decide whether to target users of Apple's iOS App Store or Android's Google Play store.