San Francisco-based Juvo came out of stealth mode last week, with a bold claim that it can make “invisible” prepaid customers visible to mobile operators, increasing their ability to monetize pay-as-you-go subscribers. Juvo’s iOS or Android app enables prepaid users to build up what is effectively a credit score, by analysing their behavior and generating a rating for the MNO. Juvo calls this an “identity score” and users can boost that rating by interacting with the app and sharing data about themselves and their habits. For the MNO, the score can be used to enable new services for prepaid subscribers (a growing percentage for many operators), including direct financial services, or (more commonly) loans of voice, data and SMS credit.…