One of the major engines behind the promising Facebook Q2 financial results was Facebook Mobile App Install Ads platform. The number of app developers that jump onto this relatively new ad platform goes up really fast. Between April and June, 8,400 advertisers purchased Facebook's mobile app install ads, compared to 3,800 advertisers the previous quarter. About 50% of the top 100 grossing apps in the Apple App Store and Google Play Store use the Facebook ad solution. According to the Fiksu data from 200 iPhone free apps traffic it monitors daily costs per loyal user -- measuring how much developers spend to acquire customers who open their apps at least three times a month -- had increased to $1.50 from $1.33 in May. Recent data from Spruce Media, a Facebook strategic Preferred Marketing Developer (PMD), showed that the app cost-per-install through advertising on Facebook increased even more to $1.67 in the second quarter from $1.57 in the prior quarter.