Mobile app usage is exploding but the lack of reliable app measurement, particularly for understanding what app audiences look like, could throw a wrench into the mobile ad spending machine. Mobile analytics firms, traditional web measurement vendors and startups aim to overcome the challenges of app audience measurement, and are coming at it in a variety of ways."The state of mobile app audience measurement is definitely becoming an impediment to faster growth of in-app advertising revenues," said Joe Laszlo, senior director of the Mobile Marketing Center of Excellence at the Int...