Only 19 percent of iPhone/iPod Touch applications in the AdMob network had more than 10,000 users in May, and a mere 5 percent had more than 100,000 users, according to the mobile ad network’s latest Mobile Metrics report. With more than 50,000 apps available on the iPhone, the long tail is in full effect — but even so, the steepness of the curve is impressive. More than half of the apps in the AdMob network had fewer than 1,000 users in May.