Google has fought predatory loans for a while, but now it's taking that fight to its app store. The Wall Street Journal has learned that Google recently banned Play Store apps with "deceptive or harmful" personal loans where the annual percentage rate is 36 percent or higher, such as many payday loans. A spokesman said the expanded financial policy, implemented in August, was meant to "protect users" against "exploitative" terms.

Apple doesn't have a similar ban, but told the WSJ that it routinely reviews its App Store rules to "address new or emerging issues."

To no one's surprise, affected lenders aren't happy - this forces them to either offer lower rates or bow out entirely. Online Lenders Alliance CEO Mary Jackson repeatedly maintained that the companies' practices were allowed, arguing that the ban hurts "legitimate operators" as well as customers looking for "legal loans."

While there won't be too many people mourning the absence of these loans, Google's decision does raise the question of whether store operators should ban apps whose business models are ethically shaky, but still legal. Much like retailers' approaches to e-cigarettes, tech giants may have enough power to decide whether or not entire business categories can succeed.