Web publishers have long lamented the lack of ad spending online in relation to the amount of time spent online. Now Flurry is making the same case for mobile. In a new study, the mobile advertising and analytics firm says mobile is the most imbalanced medium when it comes to ad spending versus time spent, at 1% compared to 23%. That makes the split of ad spending and time spent on the desktop Web -- at 16% versus 22% -- look a lot better.